Eleanor Crain McPeck, 71, co-founder of Howard R. McPeck & Co., a Washington real estate brokerage firm, and a former employe of the Office of Strategic Services (OSS), died of congestive heart failure Wednesday at her home in Washington.

During World War II, Mrs. McPeck worked in the photo reconnaissance division of the OSS, a forerunner of the Central Intelligence Agency.

In 1944, she and her husband, Howard Ripley McPeck, established their real estate brokerage firm. The firm specializes in the sale of Georgetown properties.

Born in Mount Victoria, Md., she was the daughter of Robert Crain, a former Maryland Corporation Counsel and one of the state's largest landowners. The Crain Highway, linking Baltimore and Southern Maryland, was named in his honor.

Mrs. McPeck graduated from Holton-Arms School in 1927. In 1936, she married Mr. Peck. he died in 1960.

She was a member of The Committee of 100 of the Federal City, the Citizens Assocition of Georgetown and groups supporting the Washington Cathedral. She also did volunteer work for numerous charitable organizations, including the American Red Cross and the American Cancer Society.

Survivors include a daughter, Eleanor M. McPeck of Cambridge, Mass.; a son, Howard R. McPeck of Perrsburg, Ohio; a sister, Margaret C. Downs of Baltimore, and three grandchildren.

The family suggests that expressions of sympathy be in the form of contributions to the Washington Cathedral, the Scholarship Fund at St. Alban's School for Boys, or the National Audobon Society.