John Schuck was born Conrad John Schuck in Boston, Massachusetts in 1940, the son of an English professor who took several teaching positions including Princeton College and SUNY Buffalo while John was growing up. Following graduation from Denison University where he appeared in a number of plays, John turned to regional theatre for work, including the Cleveland Playhouse, Baltimore Center Stage, and American Conservatory Theatre in San Francisco. He was discovered at ACT for film by director Robert Altman, who featured him as Painless, the dentist in the now-cult classic film MASH (1970). Altman continued to use John in Brewster McCloud (1970), McCabe & Mrs. Miller (1971), and most assuredly in Thieves Like Us (1974), arguably his best film role. On television, Schuck won a regular part as a sergeant on McMillan & Wife (1971) opposite Rock Hudson and Susan Saint James for six seasons. However, most of his work seemed mired in playing dim, simple-minded characters such as the robot on the silly short-lived comedy Holmes and Yoyo (1976) and as Herman Munster on The Munsters Today (1987), a revisit to the ghoulish 1960s television family.
Schuck is also known for his work on Star Trek movies and television series, often playing a Klingon character, as well as his recurring roles as Draal on Babylon 5 and as Chief of Detectives Muldrew of the New York City Police Department in the Law & Order programs, especially Law & Order: Special Victims Unit.