The 1950s mirrored the 1940s, with him appearing in several films and television series, at times uncredited. In 1952 he played the co-pilot in Above and Beyond. In 1955, Simmons won his best-known role, portraying Sergeant william Preston in Sergeant Preston of the Yukon. Following the end of the series in 1958, he continued to have a successful acting career, mostly in television series guest appearances, through 1982, with his last role being in CHiPs, guest-starring along with Sue Lyon and Cesar Romero.