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, Section 17(a) of the Public Utility Holding Company Act of 1935 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 * HAMLIN CLAY W III   2. Issuer Name and Ticker or Trading Symbol CORPORATE OFFICE PROPERTIES TRUST [OFC] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 6711 COLUMBIA GATEWAY DRIVE, SUITE 300 3. Date of Earliest Transaction (Month/Day/Year) 04/15/2013 (Street) COLUMBIA, MD 21046 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 Units-COPLP 04/15/2013   C   10,000 D (4) 1,057,782 I See Footnote (3) Common Shares-COPT 04/15/2013   M   10,000 A (1) 17,525 I See Footnote (2) Common Shares-COPT 04/15/2013   S   10,000 (5) D $ 28.499 7,525 D

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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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
HAMLIN CLAY W III 6711 COLUMBIA GATEWAY DRIVE SUITE 300 COLUMBIA, MD 21046	X

Signatures

Karen M. Singer, by Power of Attorney		04/17/2013
**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)	Acquired through conversion of COPLP Units.
(2)	These shares are owned as follows: 10,000 shares are owned by LBCW Limited Partnership as a result of this conversion and 7,525 shares are owned by Clay W. Hamlin, III.
(3)	The 1,057,782 units are owned as follows: 65,264 by Clay W. Hamlin, III; 871,107 by LBCW; L.P.; and 121,411 by Lynn Hamlin.
(4)	These COPLP Units were converted into Common Shares of COPT.
(5)	The sales reported in this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by LBCW, L.P. on December 14, 2011.

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