Burghoff made his feature film debut in Robert Altman's "MASH" (1970). Although several actors from the original film made guest appearances in the television series "M*A*S*H", Burghoff was the only actor to continue as a regular, in the role of Radar O'Reilly. Although he played the same character in the series as in the film, Burghoff has cited differences in the portrayal: "In the original feature film M*A*S*H, I created Radar as a lone, darker and somewhat sardonic character; kind of a shadowy figure. I continued these qualities for a short time until I realized that the TV M*A*S*H characters were developing in a different direction from the film characters. It became a group of sophisticated, highly educated doctors (and one head nurse) who would rather be anywhere else and who understood the nature of the 'hellhole' they were stuck in. With Gelbart's help, I began to mold Radar into a more innocent, naïve character as contrast to the other characters, so that while the others might deplore the immorality and shame of war (from an intellectual and judgmental viewpoint), Radar could just REACT from a position of total innocence."