Gilliam appeared in the role of "Floyd", the desk clerk in the movie Paper Moon. He has also appeared in popular motion pictures such as Blazing Saddles and Back to the Future Part III. He has had roles in several other motion pictures such as Honeymoon in Vegas, Thunderbolt and Lightfoot, Farewell, My Lovely, Fletch, Gator, Telefon, and The Terror Within II.
Gilliam is married to Susan Gilliam. They have two children together. His granddaughter his gymnast Hollie Vise.