 Ostertag, who had attained the rank of Sergeant, completed officer training and received his commission as a Second Lieutenant while serving with the 55th in France.After the war he was active in the American Legion and Veterans of Foreign Wars, and entered politics as a Republican.Ostertag was a member of the New York State Assembly (Wyoming Co.) in 1932, 1933, 1934, 1935, 1936, 1937, 1938, 1939–40, 1941–42, 1943–44, 1945–46, 1947–48 and 1949–50.