COPT DEFENSE PROPERTIES — Director's Dealing 2011

May 13, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: CORPORATE OFFICE PROPERTIES TRUST (OFC)
CIK: 0000860546
Period of Report: 2011-05-12

Reporting Person: GRIFFIN RANDALL M (Director, Chief Executive Officer)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-05-12	Common Shares of Stock	M	138068	$12.45	Acquired	565024	Direct
2011-05-12	Common Shares of Stock	S	138068	$34.221	Disposed	426956	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2011-05-12	Options of Common Stock	$12.45	M	138068	Disposed	2012-03-07	Common Shares (138068)	Direct

Footnotes

F1: As of 05-12-2011, common share holdings comprised of 95,888 owned by RMG Security Trust, 2,000 owned by Rand Griffin Non-qualified 401K plan, 198,893 unrestricted and 130,175 restricted.