FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
GRIFFIN RANDALL M
   2. Issuer Name and Ticker or Trading Symbol
CORPORATE OFFICE PROPERTIES TRUST [OFC] 		5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) __X__ Other (specify below)
President & CEO / Trustee
(Last)
(First)
(Middle)
11666 FARSIDE ROAD		 3. Date of Earliest Transaction (Month/Day/Year)
08/24/2009
(Street)

ELLICOTT CITY, MD 21042		 4. If Amendment, Date Original Filed(Month/Day/Year)
 6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)		 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)		 4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)		 5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)		 6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)		 7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
Common Shares 08/24/2009   M   6,932 A $ 7.625 514,114 (1) D  
Common Shares 08/24/2009   M   25,000 A $ 9.75 539,114 (3) D  
Common Shares 08/24/2009   S   31,932 D $ 38.138 507,182 (2) D  

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)		 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)		 5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)		 6. Date Exercisable and Expiration Date
(Month/Day/Year)		 7. Title and Amount of Underlying Securities
(Instr. 3 and 4)		 8. Price of Derivative Security
(Instr. 5)		 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)		 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)		 11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Options of Common Shares $ 7.625 08/24/2009   M     6,932 01/01/2001 01/01/2010 Common Shares 6,932 $ 7.625 243,068 D  
Options of Common Shares $ 9.75 08/24/2009   M     25,000 09/12/2001 09/12/2010 Common Shares 25,000 $ 9.75 218,068 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
GRIFFIN RANDALL M
11666 FARSIDE ROAD
ELLICOTT CITY, MD 21042		       President & CEO Trustee

Signatures

 Karen M. Singer, by Power of Attorney   08/24/2009
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1) As of 8/3/09, common share holdings comprised of 95,888 owned by RMG Security Trust, 2,525 owned by spouse and daughters, 2,000 owned by Rand Griffin Non-qualified 401K plan, 252,718 unrestricted and 160,983 restricted.
(2) As of 8/4/09, common share holdings comprised of 95,888 owned by RMG Security Trust, 2,525 owned by spouse and daughters, 2,000 owned by Rand Griffin Non-qualified 401K plan, 245,786 unrestricted and 160,983 restricted.
(3) As of 8/4/09, common share holdings comprised of 95,888 owned by RMG Security Trust, 2,525 owned by spouse and daughters, 2,000 owned by Rand Griffin Non-qualified 401K plan, 277,718 unrestricted and 160,983 restricted.

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