In 1952, he began playing Chester, the trusty jailhouse assistant to Marshal Matt Dillon on "Gunsmoke", eventually ad-libbing the character's full name, "Chester Wesley Proudfoot" (later changed to "Chester Goode" in the televised version of the series, which featured Dennis Weaver in the role of Chester). Baer's portrayal of Chester was generally considered his finest and most memorable role, and as he often said, the one he found most fulfilling. Baer also worked as a voice actor on several other radio shows produced by Norman MacDonnell, performing as Pete the Marshal on the situation comedy "The Harold Peary Show", as Doc Clemens on "Rogers of the Gazette", and as additional characters on "Fort Laramie" and "The Adventures of Philip Marlowe".