Born Marion Delbridge Moore in Pensacola, Florida, he began his career in radio before moving to television. In 1952, he appeared in the first of several So You Want To… Warner Bros. comedy shorts with George O'Hanlon. He co-starred in the early television comedy Life with Elizabeth (1953-1955) opposite Betty White. A good friend of Jack Webb, he appeared in many episodes of Dragnet and Adam 12. For several years in the late 1950s he hosted a daily children's program on KTTV Channel 11 opposite Willy the Wolf (a muppet-like adult size character) in a daily children's show on KTTV Channel 11 in Los Angeles.
Moore played supporting roles in several Jerry Lewis films, including The Big Mouth and The Patsy. He made his feature-film debut in Lewis' Cinderfella in 1960, the university president, in 1963's The Nutty Professor. He was also in the 1967 teen film Catalina Caper, which later appeared as an "experiment" in a 1990 episode of Mystery Science Theater 3000.