In 1957, he appeared in Sidney Lumet's "12 Angry Men" as the abrasive Juror #3. In 1959, on CBS' "DuPont Show of the Month", he starred in the dual roles of Miguel de Cervantes and Don Quixote in the play "I, Don Quixote", which years later became the musical "Man of La Mancha". Cobb also appeared as the Medicine Bow, Wyoming owner of the Shiloh Ranch, Judge Henry Garth in the first four seasons (1962–1966), of the long-running NBC Western television series "The Virginian" (1962–1971).