After his service he attended Northwestern University, where he was a Phi Gamma Delta fraternity brother, and graduated with a bachelor's degree in theater arts.

[1] Afterward, he worked at a radio station, played a clown on a live TV show in Dallas, became an assistant athletic director at Northwestern, and sold medical supplies and insurance.

Before becoming a star, Stevenson appeared as a contestant on the Password television game show in New York City, winning five pieces of luggage.

After guest-starring in That Girl with Marlo Thomas, he was cast in The Doris Day Show in 1969, playing magazine editor boss Michael Nicholson until 1971.

Stevenson found his greatest success in M*A*S*H. The series quickly became one of the most popular situation comedies of its time, and was eventually recognized as one of the top sitcoms in television history.

Colonel Blake was discharged, only to board a plane that was shot down over the Sea of Japan, killing everyone on board—a development added after scripts were distributed so the show's actors would display genuine emotion.

"[6] Although he had played ensemble parts for several years, he stated that the primary reasons for his departure were systemic problems with 20th Century Fox, especially disregard for simple comforts for cast and crew on location,[7] and the more lucrative opportunities presented to him at the time.

[12] During the 1988–89 television season, he returned to a supporting TV role in an ensemble, playing Max Kellerman in the short-lived CBS series adaptation of Dirty Dancing.

Steve Daley wrote in 1985 that he had "worn out his television welcome",[14] while David Bianculli drafted "The Annual McLean Stevenson Memorial 'I'm Gonna Quit This Show and Become a Big Star' Award" early in his career as a critic.

"[16] Stevenson's screen credits include the Disney movie The Cat from Outer Space as a friend of Frank Wilson (played by Ken Berry) along with his M*A*S*H replacement Harry Morgan.

[17] Stevenson was recovering from bladder cancer surgery at the Encino-Tarzana Regional Medical Center on February 15, 1996, when he suffered a sudden fatal heart attack.

[20] By coincidence, Roger Bowen, who portrayed Henry Blake in the 1970 movie M*A*S*H, died of a heart attack the day after Stevenson's death.