While a member of the Seventy-seventh Congress, Osmers enlisted as a private and graduated from the Infantry School at Fort Benning, Georgia, as a second lieutenant. He was placed on the inactive list by Presidential directive and finished his term in Congress, but was not a candidate for reelection in 1942 to the Seventy-eighth Congress.
Osmers went on active duty as a second lieutenant in the Seventy-seventh Infantry Division on January 4, 1943, transferred to the Twenty-fourth Corps and served in the Pacific, and was discharged on February 22, 1946. He served as a major in Officers’ Reserve Corps.
After he returned from his military service, Osmers resumed his former business pursuits and was also interested in real estate, insurance, and publishing businesses. He was elected as a Republican to the Eighty-second Congress, by special election on November 6, 1951, to fill the vacancy caused by the resignation of Harry L. Towe, and was reelected to the six succeeding Congresses, serving from November 6, 1951, to January 3, 1965. Osmers voted in favor of the Civil Rights Acts of 1957,[2]1960,[3] and 1964,[4] and the 24th Amendment to the U.S. Constitution.[5] He was an unsuccessful candidate for reelection in 1964 to the Eighty-ninth Congress, and was again unsuccessful in his bid for office in 1966 to the Ninetieth Congress, both times losing to Democrat Henry Helstoski by 51% to 49% margins.
^"Haworth Notes", The Record, September 16, 1924. Accessed February 20, 2024, via Newspapers.com. "Frank C. Osmers, Jr., son of Mr. and Mrs. Frank C. Osmers of Washington avenue, left Saturday morning for Williamstown, Mass., where he will enter the freshman year in Williams College.... Frank is a graduate of Dumont High school and was once a correspondent for this paper."