UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM N-Q

QUARTERLY SCHEDULE OF PORTFOLIO HOLDINGS OF REGISTERED
MANAGEMENT INVESTMENT COMPANY

Investment Company Act file number 811-21280

Name of Fund: BlackRock Preferred Opportunity Trust (BPP)

Fund Address: 100 Bellevue Parkway, Wilmington, DE 19809

Name and address of agent for service: Donald C. Burke, Chief Executive Officer, BlackRock Preferred Opportunity Trust, 800 Scudders Mill Road, Plainsboro, NJ, 08536. Mailing address: P.O. Box 9011, Princeton, NJ, 08543-9011

Registrant’s telephone number, including area code: (800) 882-0052, Option 4

Date of fiscal year end: 12/31/2008

Date of reporting period: 01/01/2008 – 03/31/2008

Item 1 – Schedule of Investments

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
      Shares   Exchange-Traded Funds     Value  
      150,000   UltraShort Financials ProShares   $ 17,647,500  
          Total Exchange-Traded Funds (Cost - $18,385,600) - 5.4%     17,647,500  
          Preferred Securities        
      Par            
Industry     (000)   Capital Trusts        
Capital Markets - 2.1%   $ 1,920   State Street Capital Trust III, 8.25% (a)(b)     1,894,035  
      6,725   State Street Capital Trust IV, 3.80%, 6/01/67 (a)     5,037,563  
                6,931,598  
Commercial Banks - 7.7%     1,425   Abbey National Capital Trust I, 8.963% (a)(b)     1,686,466  
      9,150   BB&T Capital Trust IV, 6.82%, 6/12/77 (a)     7,555,329  
      3,185   Barclays Bank Plc, 5.926% (a)(b)(c)     2,731,440  
      450   Dresdner Funding Trust I, 8.151%, 6/30/31 (c)     397,823  
      1,100   FCB/NC Capital Trust I, 8.05%, 3/01/28     1,144,330  
      1,925   Huntington Capital III, 6.65%, 5/15/37 (a)     1,479,767  
      2,000   NBP Capital Trust III, 7.375% (b)     1,840,000  
      5,600   Wachovia Corp. Series K, 7.98% (a)(b)     5,502,000  
      3,000   Westpac Capital Trust IV, 5.256% (a)(b)(c)     2,660,250  
                24,997,405  
Diversified Financial     2,670   JPMorgan Chase Capital XXIII, 4.065%, 5/15/77 (a)     2,025,710  
Services - 0.6%                  
Insurance - 5.6%     4,500   AFC Capital Trust I Series B, 8.207%, 2/03/27     3,513,353  
      9,605   American General Institutional Capital A, 7.57%, 12/01/45 (c)     9,412,660  
      5,000   Mangrove Bay Pass-Through Trust, 6.102%, 7/15/33 (a)(c)     3,681,700  
      1,800   Zenith National Insurance Capital Trust I, 8.55%, 8/01/28 (c)     1,804,500  
                18,412,213  
Thrifts & Mortgage     1,925   Webster Capital Trust IV, 7.65%, 6/15/37 (a)     1,311,766  
Finance - 0.4%                  
          Total Capital Trusts        
          (Cost - $63,778,603) - 16.4%     53,678,692  
      Shares   Preferred Stocks        
Capital Markets - 1.2%     75,000   The Bear Stearns Cos., Inc. Series E, 6.15%     2,943,750  
      31,100   Lehman Brothers Holdings Inc. Series D, 5.67%     1,045,271  
                3,989,021  
Commercial Banks - 10.0%     30,000   Banesto Holdings, Ltd. Series A, 10.50%     947,814  
      120,000   First Republic Preferred Capital Corp., 7.25%     2,250,000  
      50,000   HSBC USA, Inc. Series H, 6.50%     1,125,000  
      255,200   NB Capital Corp. Series DEP, 8.35%     5,484,248  
      248,000   Santander Finance Preferred SA Unipersonal, 6.50%     5,262,262  
      60,000   Santander Finance Preferred SA Unipersonal, 6.80%     1,336,878  
      30   SunTrust Real Estate Investment Trust, 9%     3,120,000  
      60   Union Planter Preferred Funding Corp., 7.75% (c)     6,686,250  

1

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
Industry       Shares     Preferred Stocks     Value  
      261,800   Wachovia Corp. Series J, 8%   $ 6,466,460  
                32,678,912  
Diversified Financial     109,000   Bank of America Corp., 6.625%     2,463,400  
Services - 4.3%     245,000   Citigroup, Inc. Series AA, 8.125%     5,889,800  
      120,000   Citigroup, Inc. Series T, 6.50% (d)     5,697,600  
                14,050,800  
Electric Utilities - 0.4%     50,000   Alabama Power Co., 6.50%     1,237,500  
Electrical Equipment - 0.2%     787,326   Superior Essex Holding Corp. Series A, 9.50%     590,495  
Insurance - 11.1%     298,400   ACE Ltd. Series C, 7.80%     7,382,416  
      117,414   Arch Capital Group Ltd. Series A, 8%     2,996,405  
      115,000   Aspen Insurance Holdings Ltd., 7.401% (a)     2,478,250  
      172,400   Endurance Specialty Holdings Ltd. Series A, 7.75%     4,053,124  
      274,500   Metlife, Inc. Series B, 6.50%     6,297,030  
      209,400   PartnerRe Ltd. Series C, 6.75%     4,757,568  
      62,000   Prudential Plc, 6.50%     1,451,420  
      235,000   RenaissanceRe Holding Ltd. Series D, 6.60%     4,852,750  
      2,000   Zurich RegCaPS Funding Trust, 6.58% (a)(c)     2,010,000  
                36,278,963  
Oil, Gas & Consumable     5,000   Devon Energy Corp. Series A, 6.49%     504,688  
Fuels - 0.2%                  
Real Estate Investment Trusts     60,000   Chevy Chase Preferred Capital Corp. Series A, 10.375%     3,060,000  
(REITs) - 2.0%     3,180   Sovereign Real Estate Investment Corp., 12%     3,561,600  
                6,621,600  
Thrifts & Mortgage     265,000   Fannie Mae, 8.25%     6,373,250  
Finance - 6.4%     202,000   Freddie Mac Series Q, 3.85% (a)     5,454,000  
      100,000   Freddie Mac Series U, 5.90%     2,067,000  
      85,300   Freddie Mac Series Y, 6.55%     1,914,985  
      110,000   Freddie Mac Series Z, 8.375%     2,684,000  
      30   Roslyn Real Estate Asset Corp. Series C, 8.95%     2,630,625  
                21,123,860  
          Total Preferred Stocks        
          (Cost - $131,914,565) - 35.8%     117,075,839  
      Par            
      (000)   Trust Preferreds        
Capital Markets - 0.7%   $ 278   Structured Asset Trust Unit Repackagings (SATURNS), Credit Suisse First Boston (USA), Inc. Debenture Backed Series 2003-13, 6.25%, 7/15/32     238,872  
      2,573   Structured Asset Trust Unit Repackagings (SATURNS), Goldman Sachs Group, Inc. Debenture Backed Series 2003-06, 6%, 2/15/33     2,170,206  
                2,409,078  
Commercial Banks - 1.1%     2,000   Colonial Capital Trust IV, 7.875%, 10/01/33     1,578,269  
      2,930   Keycorp Capital V, 5.875%, 7/30/33     2,076,286  
                3,654,555  

2

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
      Par            
Industry     (000)   Trust Preferreds     Value  
Diversified Financial   $ 278   PPLUS Trust Certificates Series VAL-1 Class A, 7.25%,        
Services - 0.1%         4/15/32   $ 264,769  
Food Products - 0.7%     2,500   Corporate-Backed Trust Certificates, Kraft Foods, Inc.        
          Debenture Backed Series 2003-11, 5.875%, 11/01/31        
                2,226,802  
Insurance - 0.9%     750   Everest Re Capital Trust, 6.20%, 3/29/34     599,373  
      380   Financial Security Assurance Holdings Ltd., 5.60%, 7/15/03     296,166  
      460   PLC Capital Trust IV, 7.25%, 9/25/32     434,334  
      1,985   The Phoenix Cos., Inc., 7.45%, 1/15/32     1,586,500  
                2,916,373  
Media - 3.6%     1,250   Comcast Corp., 7%, 9/15/55     1,169,607  
      11,750   Comcast Corp., 6.625%, 5/15/56     10,519,003  
      180   Corporate-Backed Trust Certificates, News America Debenture Backed Series 2002-9, 8.125%, 12/01/45     171,677  
                11,860,287  
Oil, Gas & Consumable     3,875   Nexen, Inc., 7.35%, 11/01/43     3,670,982  
Fuels - 1.1%                  
Wireless Telecommunication     2,586   Structured Repackaged Asset-Backed Trust Securities,        
Services - 0.5%         Sprint Capital Corp. Debenture Backed Series 2004-2,        
          6.50%, 11/15/28     1,539,579  
          Total Trust Preferreds        
          (Cost - $32,719,286) - 8.7%     28,542,425  
          Total Preferred Securities        
          (Cost - $228,412,454) - 60.9%     199,296,956  
          Fixed Income Securities        
          Corporate Bonds        
Aerospace & Defense - 0.1%     90   CHC Helicopter Corp., 7.375%, 5/01/14     89,662  
      170   Hexcel Corp., 6.75%, 2/01/15     164,475  
      160   TransDigm, Inc., 7.75%, 7/15/14     160,000  
                414,137  
Auto Components - 0.1%     350   Lear Corp., 8.75%, 12/01/16     298,812  
      125   Metaldyne Corp., 10%, 11/01/13     75,000  
                373,812  
Building Products - 0.6%     1,945   C8 Capital SPV Ltd., 6.64% (a)(b)(c)     1,794,613  
      260   CPG International I, Inc., 10.50%, 7/01/13     218,400  
                2,013,013  
Capital Markets - 3.4%     3,850   The Bear Stearns Cos., Inc., 6.40%, 10/02/17     3,801,494  
      3,880   Credit Suisse Guernsey Ltd., 5.86% (a)(b)     3,286,860  
      650   Lehman Brothers Holdings, Inc., 4.50%, 9/15/22 (a)     598,243  

3

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
      Par            
Industry     (000)   Corporate Bonds     Value  
                                              $ 3,875   Lehman Brothers Holdings, Inc., 6.875%, 7/17/37   $ 3,359,815  
                11,046,412  
Chemicals - 0.2%     200   American Pacific Corp., 9%, 2/01/15     194,500  
      30   Chemtura Corp., 6.875%, 6/01/16     26,700  
      630   Key Plastics LLC, 11.75%, 3/15/13 (c)     453,600  
                674,800  
Commercial Banks - 24.4%     12,175   BNP Paribas, 7.195% (a)(b)(c)(e)     10,783,020  
      4,015   Bank of Ireland Capital Funding II, LP, 5.571% (a)(b)(c)     3,170,224  
      4,275   Bank of Ireland Capital Funding III, LP, 6.107% (a)(b)(c)     3,253,891  
      2,600   Barclays Bank Plc, 7.434% (a)(b)(c)     2,350,618  
      5,000   CBA Capital Trust I, 5.805% (b)(c)     4,691,400  
      16,385   Credit Agricole SA, 6.637% (a)(b)(c)     12,692,460  
      6,399   Lloyds TSB Bank Plc, 6.90% (b)     6,079,050  
      4,000   RESPARCS Funding LP I, 8% (b)     3,454,400  
      2,775   Royal Bank of Scotland Group Plc, 6.99% (a)(b)(c)     2,355,697  
      1,960   Royal Bank of Scotland Group Plc, 7.648% (a)(b)     1,870,669  
      3,700   Royal Bank of Scotland Group Plc Series MTN, 7.64% (a)(b)     3,186,403  
      3,185   Skandinaviska Enskilda Banken AB, 4.958% (a)(b)(c)     2,852,903  
      5,000   Skandinaviska Enskilda Banken AB, 5.471% (a)(b)(c)     4,511,985  
      10,575   Societe Generale, 5.922% (a)(b)(c)     8,633,853  
      4,925   Standard Chartered Bank, 7.014% (a)(b)(c)     4,287,587  
      5,000   Sumitomo Mitsui Banking Corp., 5.625% (a)(b)(c)     4,229,105  
      2,050   SunTrust Preferred Capital I, 5.853% (a)(b)     1,519,317  
                79,922,582  
Commercial Services &     100   FTI Consulting, Inc., 7.75%, 10/01/16     103,500  
Supplies - 0.0%                  
Containers & Packaging - 0.3%     195   Berry Plastics Holding Corp., 6.675%, 9/15/14 (a)     154,050  
      340   Berry Plastics Holding Corp., 8.875%, 9/15/14     296,650  
      385   Crown Americas LLC, 7.75%, 11/15/15     395,587  
      240   Impress Holdings BV, 5.838%, 9/15/13 (a)(c)     199,200  
                1,045,487  
Diversified Financial     8,900   Bank of America Corp. Series K, 8% (a)(b)     8,910,680  
Services - 7.6%     7,730   JPMorgan Chase Capital XXI Series U, 4.062%, 2/02/37 (a)     5,697,265  
      11,125   JPMorgan Chase Capital XXV, 6.80%, 10/01/37     10,164,657  
                24,772,602  
Diversified Telecommunication     290   Cincinnati Bell, Inc., 7.25%, 7/15/13     284,925  
Services - 1.1%     1,705   Qwest Communications International, Inc., 7.50%, 2/15/14     1,602,700  
      460   Qwest Corp., 6.05%, 6/15/13 (a)     414,000  
      420   Wind Acquisition Finance SA, 10.75%, 12/01/15 (c)     428,400  

4

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
      Par            
Industry     (000)   Corporate Bonds     Value  
                                              $ 640   Windstream Corp., 8.125%, 8/01/13   $ 628,800  
      290   Windstream Corp., 8.625%, 8/01/16     284,925  
                3,643,750  
Electric Utilities - 0.8%     175   Edison Mission Energy, 7.50%, 6/15/13     179,375  
      17   Midwest Generation LLC Series B, 8.56%, 1/02/16     18,115  
      2,675   PPL Capital Funding, 6.70%, 3/30/67 (a)     2,274,740  
                2,472,230  
Electrical Equipment - 0.1%     425   Superior Essex Communications LLC, 9%, 4/15/12     409,063  
Electronic Equipment &     140   Sanmina-SCI Corp., 6.75%, 3/01/13     121,450  
Instruments - 0.3%     1,155   Sanmina-SCI Corp., 8.125%, 3/01/16     1,022,175  
                1,143,625  
Energy Equipment &     70   Compagnie Generale de Geophysique-Veritas,        
Services - 0.2%         7.50%, 5/15/15     71,050  
      100   Grant Prideco, Inc. Series B, 6.125%, 8/15/15     102,250  
      350   SemGroup LP, 8.75%, 11/15/15 (c)     320,250  
                493,550  
Gas Utilities - 0.1%     420   Targa Resources, Inc., 8.50%, 11/01/13     386,400  
Hotels, Restaurants &     415   American Real Estate Partners LP, 7.125%, 2/15/13     376,612  
Leisure - 0.3%     385   Greektown Holdings, LLC, 10.75%, 12/01/13 (c)     350,350  
      60   Universal City Florida Holding Co. I, 7.989%, 5/01/10 (a)     58,200  
      40   Wynn Las Vegas LLC, 6.625%, 12/01/14     38,500  
                823,662  
IT Services - 0.0%     100   SunGard Data Systems, Inc., 9.125%, 8/15/13     101,000  
      36   SunGard Data Systems, Inc., 10.25%, 8/15/15 (c)     36,180  
                137,180  
Insurance - 33.6%     7,150   AXA SA, 6.379% (a)(b)(c)     5,763,408  
      6,350   The Allstate Corp., 6.50%, 5/15/57 (a)     5,229,453  
      5,200   The Allstate Corp. Series B, 6.125%, 5/15/67 (a)     4,788,108  
      5,555   American International Group, Inc., 6.25%, 3/15/87     4,500,133  
      9,025   Chubb Corp., 6.375%, 3/29/67 (a)     8,406,616  
      7,135   Everest Reinsurance Holdings, Inc., 6.60%, 5/01/67 (a)     6,013,949  
      1,475   Genworth Financial, Inc., 6.15%, 11/15/66 (a)     1,231,935  
      9,000   Kingsway America, Inc., 7.50%, 2/01/14     8,233,552  
      5,025   Liberty Mutual Group, Inc., 7%, 3/15/37 (a)(c)     4,493,114  
      3,370   Lincoln National Corp., 7%, 5/17/66 (a)     3,090,216  
      2,500   Lincoln National Corp., 6.05%, 4/20/67 (a)     2,185,810  
      6,375   Metlife, Inc., 6.40%, 12/15/66     5,065,830  
      4,850   Nationwide Life Global Funding I, 6.75%, 5/15/67     4,036,267  
      2,850   PartnerRe Finance II, 6.44%, 12/01/66 (a)     2,427,767  

5

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
     
Par
           
Industry     (000)   Corporate Bonds     Value  
    $ 5,775   Progressive Corp., 6.70%, 6/15/37 (a)   $ 5,143,336  
      6,000   Prudential Plc, 6.50% (b)     5,025,000  
      4,250   QBE Capital Funding II LP, 6.797% (a)(b)(c)     3,850,245  
      1,300   Reinsurance Group of America, 6.75%, 12/15/65 (a)     1,140,426  
      9,425   Swiss Re Capital I LP, 6.854% (a)(b)(c)     8,770,566  
      11,350   The Travelers Cos., Inc., 6.25%, 3/15/67 (a)     10,010,972  
      2,600   White Mountains Re Group Ltd., 7.506% (a)(b)(c)     2,001,693  
      650   ZFS Finance (USA) Trust IV, 5.875%, 5/09/32 (a)     614,777  
      8,765   ZFS Finance (USA) Trust V, 6.50%, 5/09/67 (a)(c)     7,909,852  
                109,933,025  
Leisure Equipment &     250   Quiksilver, Inc., 6.875%, 4/15/15     201,250  
Products - 0.1%                  
Machinery - 0.1%     460   AGY Holding Corp., 11%, 11/15/14 (c)     414,000  
Marine - 0.1%     211   Navios Maritime Holdings, Inc., 9.50%, 12/15/14 (c)     210,209  
Media - 3.1%     475   Affinion Group, Inc., 10.125%, 10/15/13     472,031  
      230   Affinion Group, Inc., 11.50%, 10/15/15     221,950  
      110   CMP Susquehanna Corp., 9.875%, 5/15/14 (c)     75,900  
      230   Cablevision Systems Corp. Series B, 7.133%, 4/01/09 (a)     228,275  
      110   Comcast Holdings Corp., 2%, 11/15/29 (d)     4,145,900  
      1,050   Dex Media West LLC, 9.875%, 8/15/13     913,500  
      175   DirecTV Holdings LLC, 8.375%, 3/15/13     177,406  
      200   EchoStar DBS Corp., 5.75%, 10/01/08     199,000  
      56   EchoStar DBS Corp., 7%, 10/01/13     52,780  
      75   EchoStar DBS Corp., 7.125%, 2/01/16     69,937  
      500   Intelsat Bermuda Ltd., 9.25%, 6/15/16     503,750  
      590   Intelsat Corp., 9%, 6/15/16     594,425  
      210   Intelsat Subsidiary Holding Co. Ltd., 8.625%, 1/15/15     211,575  
      1,195   Nielsen Finance LLC, 10%, 8/01/14     1,189,025  
      65   PanAmSat Corp., 9%, 8/15/14     65,487  
      350   Paxson Communications Corp., 5.963%, 1/15/12 (a)(c)     283,500  
      240   R.H. Donnelley Corp. Series A-3, 8.875%, 1/15/16     151,800  
      902   Windstream Regatta Holdings, Inc., 11%, 12/01/17 (c)     550,220  
                10,106,461  
Metals & Mining - 0.8%     940   AK Steel Corp., 7.75%, 6/15/12     948,225  
      200   Freeport-McMoRan Copper & Gold, Inc., 5.883%, 4/01/15 (a)     196,500  
      1,450   Freeport-McMoRan Copper & Gold, Inc., 8.375%, 4/01/17     1,538,813  
                2,683,538  

6

BlackRock Preferred Opportunity Trust        
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
      Par            
Industry     (000)   Corporate Bonds     Value  
Multi-Utilities - 0.3%   $ 925   Puget Sound Energy, Inc. Series A, 6.974%, 6/01/67 (a)   $ 833,625  
Oil, Gas & Consumable     180   Berry Petroleum Co., 8.25%, 11/01/16     184,050  
Fuels - 1.6%     220   Chaparral Energy, Inc., 8.50%, 12/01/15     191,400  
      30   Chesapeake Energy Corp., 6.875%, 11/15/20     29,100  
      80   Compton Petroleum Finance Corp., 7.625%, 12/01/13     76,600  
      75   EXCO Resources, Inc., 7.25%, 1/15/11     72,938  
      550   OPTI Canada, Inc., 8.25%, 12/15/14     544,500  
      350   Sabine Pass LNG LP, 7.50%, 11/30/16     337,750  
      4,325   TransCanada PipeLines Ltd., 6.35%, 5/15/67 (a)     3,822,798  
      55   Whiting Petroleum Corp., 7.25%, 5/01/13     54,175  
                5,313,311  
Paper & Forest Products -     80   Domtar Corp., 7.125%, 8/15/15     75,400  
0.1%     270   NewPage Corp., 10%, 5/01/12     274,050  
                349,450  
Real Estate Investment Trusts     2,000   Rouse Co. LP, 5.375%, 11/26/13     1,565,610  
(REITs) - 0.5%                  
Road & Rail - 0.0%     30   Avis Budget Car Rental LLC, 5.565%, 5/15/14 (a)     23,550  
Specialty Retail - 0.6%     190   AutoNation, Inc., 4.713%, 4/15/13 (a)     155,800  
      190   AutoNation, Inc., 7%, 4/15/14     168,625  
      1,199   Lazy Days' R.V. Center, Inc., 11.75%, 5/15/12     953,205  
      610   Michaels Stores, Inc., 10%, 11/01/14     533,750  
                1,811,380  
Thrifts & Mortgage Finance - 0.2%     1,400   Washington Mutual Preferred Funding Delaware, 6.534% (a)(b)(c)     737,730  
Wireless Telecommunication     845   Nordic Telephone Co. Holdings ApS, 8.875%,        
Services - 0.2%         5/01/16 (c)     819,650  
          Total Corporate Bonds        
          (Cost - $299,921,984) - 80.9%     264,878,594  
          Short-Term Securities        
      4,000   Federal Home Loan Bank, 1.50%, 4/01/08     4,000,000  
      45,300   Federal Home Loan Bank, 1.85%, 4/02/08     45,297,836  
      1,000   Federal Home Loan Bank, 1.80%, 4/18/08     999,178  
          Total Short-Term Securities        
          (Cost - $50,297,014) - 15.4%     50,297,014  
          Total Investments        
          (Cost - $597,017,052*) - 162.6%     532,120,064  
          Other Assets Less Liabilities - 4.9%     16,069,245  
          Preferred Shares, at Redemption Value - (67.5%)     (220,911,832 )
          Net Assets Applicable to Common Shares - 100.0%   $ 327,277,477  

7

BlackRock Preferred Opportunity Trust
Schedule of Investments as of March 31, 2008 (Unaudited) (Percentages shown are based on Net Assets)
     
     
*   The cost and unrealized appreciation (depreciation) of investments as of March 31, 2008, as
    computed for federal income tax purposes, were as follows:
    Aggregate cost   $   597,017,052    
    Gross unrealized appreciation   $   2,700,614    
    Gross unrealized depreciation       (67,533,385 )  
    Net unrealized depreciation   $   (64,832,771 )  
(a)   Floating rate security. Rate shown is as of report date.
(b)   Security is a perpetual in nature and has no stated maturity date. In certain instances, a final
    maturity date may be extended and/or the final payment may be deferred at the issuer's option
    for a specified time without default.
(c)   Security exempt from registration under Rule 144A of the Securities Act of 1933. These securities may
    be resold in transactions exempt from registration to qualified institutional investors. The Fund is not
    obligated for costs associated with the registration of restricted securities.
(d)   Convertible security.
(e)   All or a portion of security, with a market value of $4,516,866 have been pledged as collateral in
    connection with open financial futures contracts.

•   Financial futures contracts purchased as of March 31, 2008 were as follows:  
            Expiration     Face       Unrealized
    Contracts   Issue   Date     Value       Appreciation
    783   2-Year U.S. Treasury Bond   June 2008   $ 167,720,288     $ 355,556  
    Total Unrealized Appreciation     $ 355,556  
         
•   Financial futures contracts sold as of March 31, 2008 were as follows:  
                          Unrealized
            Expiration     Face       Appreciation
    Contracts   Issue   Date     Value       (Depreciation)
    246   10-Year U.S. Treasury Bond   June 2008   $ 29,311,897     $ 49,428  
    589   30-Year U.S. Treasury Bond   June 2008   $ 70,169,993       (198,634 )
    Total Unrealized Depreciation - Net     $ (149,206 )
 
•   Swaps outstanding as of March 31, 2008 were as follows:  
                  Notional       Unrealized
                  Amount       Appreciation
                  (000)       (Depreciation)
    Bought credit default protection on Dow Jones CDX                
    North America Investment Grade High Volatility                
    Index Series 9 and pay 1.40%                
                     
    Broker, Lehman Brothers Special Financing                
    Expires December 2012   $ 10,000     $ (207,661 )
 
    Bought credit default protection on Dow Jones CDX                
    North America Investment Grade High Volatility                
    Index Series 9 and pay 1.40%                
                     
    Broker, Deutsche Bank AG London                
    Expires December 2012   $ 10,000       (200,584 )

8

  BlackRock Preferred Opportunity Trust                
  Schedule of Investments as of March 31, 2008 (Unaudited)   (Percentages shown are based on Net Assets)
      Notional   Unrealized
      Amount   Appreciation
      (000)   (Depreciation)
  Bought credit default protection on Capital One                
  Financial Corp. and pay 4.175%                
                   
  Broker, Citibank, NA                
  Expires March 2013   $ 2,000     $ (61,880 )
 
  Bought credit default protection on Capital One Financial Corp. and pay 4.20%                
                   
  Broker, Deutsche Bank AG London                
  Expires March 2013   $ 1,000       (31,950 )
 
  Bought credit default protection on American                
  Express Company and pay 2.11%                
                   
  Broker, Deutsche Bank AG London                
  Expires March 2013   $ 4,000       (63,372 )
 
  Bought credit default protection on Lehman                
  Brothers Holdings, Inc. and pay 4.95%                
                   
  Broker, Deutsche Bank AG London                
  Expires March 2013   $ 2,000       (162,790 )
 
  Bought credit default protection on Kimco Realty                
  Corp. and pay 2.40%                
                   
  Broker, Goldman Sachs International                
  Expires March 2018   $ 3,000       (24,399 )
 
  Bought credit default protection on Mack-Cali Realty,                
  L.P. and pay 3.10%                
                   
  Broker, Goldman Sachs International                
  Expires March 2018   $ 1,000       23,270  
 
  Bought credit default protection on ERP Operating                
  Limited Partnership and pay 2.35%                
                   
  Broker, Goldman Sachs International                
  Expires March 2018   $ 3,000       84,117  
  Total           $ (645,249 )

9

BlackRock Preferred Opportunity Trust

    • Effective January 1, 2008, the BlackRock Preferred Opportunity Trust (the “Trust”) adopted FASB Statement of Financial Accounting Standards No. 157, “Fair Value Measurements” (“FAS 157”). FAS 157 clarifies the definition of fair value, establishes a framework for measuring fair values and requires additional disclosures about the use of fair value measurements. Various inputs are used in determining the fair value of investments, which are as follows:

     
       

    • Level 1 – price quotations in active markets/exchanges for identical securities

     
       

    • Level 2 – other observable inputs (including, but not limited to: quoted prices for similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the assets or liabilities (such as interest rates, yield curves, volatilities, prepayment speeds, loss severities, credit risks, and default rates) or other market–corroborated inputs)

     
       

    • Level 3 – unobservable inputs based on the best information available in the circumstance, to the extent observable inputs are not available (including the Trust’s own assumptions used in determining the fair value of investments)

     

    The inputs or methodology used for valuing securities are not necessarily an indication of the risk associated with investing in those securities. For information about the Trust’s policy regarding valuation of investments and other significant accounting policies, please refer to the Trust’s most recent financial statements as contained in its annual report.

    The following table summarizes the inputs used as of March 31, 2008 in determining the fair valuation of the Trust’s investments:

      Valuation   Investments in   Other Financial  
      Inputs   Securities   Instruments*  
      Level 1 $ 116,534,236 $ 206,350  
      Level 2   415,585,828   (645,249 )
      Level 3   0   0  
      Total $ 532,120,064 $ (438,899 )
    *Other financial instruments are derivative instruments such as futures and swaps.  

    10


    Item 2 – Controls and Procedures

    2(a) –

    The registrant’s principal executive and principal financial officers or persons performing similar functions have concluded that the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Investment Company Act of 1940, as amended (the “1940 Act”)) are effective as of a date within 90 days of the filing of this report based on the evaluation of these controls and procedures required by Rule 30a-3(b) under the 1940 Act and Rule 13a-15(b) under the Securities Exchange Act of 1934, as amended.

       
    2(b) –

    There were no changes in the registrant’s internal control over financial reporting (as defined in Rule 30a-3(d) under the 1940 Act) that occurred during the registrant’s last fiscal quarter that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

    Item 3 – Exhibits

    Certifications – Attached hereto

    Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

    BlackRock Preferred Opportunity Trust
     
    By:
    /s/ Donald C. Burke
      Donald C. Burke
      Chief Executive Officer of
      BlackRock Preferred Opportunity Trust
     
    Date: May 22, 2008

    Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

    By:
    /s/ Donald C. Burke
      Donald C. Burke
      Chief Executive Officer (principal executive officer) of
      BlackRock Preferred Opportunity Trust
     
    Date: May 22, 2008
     
    By:
    /s/ Neal J. Andrews
      Neal J. Andrews
      Chief Financial Officer (principal financial officer) of
      BlackRock Preferred Opportunity Trust
     
    Date: May 22, 2008

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