In 1952, he began playing Chester, the unofficial deputy to Marshal Matt Dillon on Gunsmoke, eventually ad-libbing the character's full name, "Chester Wesley Proudfoot". (The character's name was changed to "Chester Goode" in the television series, which featured an entirely different cast.) 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 worked on several other radio shows produced by Norman MacDonnell, including the situation comedy The Harold Peary Show (aka Honest Harold) as Pete the Marshal, Rogers of the Gazette (loosely based on the early life of Will Rogers) as Doc Clemens, Fort Laramie, and The Adventures of Philip Marlowe.