Former Rep. Frank C. Osmers (R-N.J.), an isolationist who enlisted in the Army as a private two days after the attack on Pearl Harbor, died Saturday at his home in Tenafly. He was 69.

Despite his isolationist stand, he had vowed to enlist if this country was attacked and he voted in Congress for war immediately after the japanese strike.

Rep. Osmers, who had first been elected to Congress in 1938 and re-elected in 1940, did not seek re-election in 1942.

Instead, he remained on duty with the infantry, rose to the rank of major and participated in the Philippine and Okinawa invasions and the Korean occupation before his discharge in 1946. He remained in the Army Reserves.

In 1951, Rep. Osmers returned to Congress after a special election to fill a vacancy. He represented his Bergen County district until the 1964 election, when he was unseated by Henry Helstoski, a Democrat.

Born in Leonia, N.J., Rep. Osmers attended Williams College. A fem expert and appraiser, he went into the jewelry business. Later he also was in real estate, insurance and publishing.

Before his election to Congress, he had served as mayor of Haworth, N.J. and as a member of the State House of Assembly.

He is survived by his wife, Marguerite Udall Osmers, of the home; a son, Frank C. III, and a daughter, Nancy Wysocki, both of Haworth; a sister, Elinor Buck, and four grandchildren.