Johnson began as a champion rodeo performer. In 1943 he was persuaded by Howard Hughes to leave his ranch and work as a horse wrangler for the film The Outlaw (1943), going on to work as a double and stuntman in Westerns. Eventually director John Ford decided to cast him in his films, and from 1949 he frequently appeared in Westerns as a supporting player and character actor, whether playing a hero or villain; ocasionally starred in films. Johnson was first onscreen as an actor in Three Godfathers (1949). For his performance as the thoughtful pool-hall owner in Peter Bogdanovich's The Last Picture Show (1971) he won a Best Supporting Actor Oscar and the New York Film Critics Award.