Coming to film from radio Westerns, Kennedy penned "Seven Men from Now" (1956), the first of four collaborations with director Budd Boetticher and the first of three with producer-director Andrew V. McLaglen. Moving from the typewriter to the director's chair by the early 1960s, Kennedy continued for a time creating lean, leathery B's and TV Westerns. He also received acclaim for his gritty WWII action drama, "Combat" (ABC, 1962-67).

Kennedy's traditional action fare brandished occasional laconic comic touches, but it was really with "The Rounders" (1965) and its spin-off TV series that comedy came to the fore in his work. "The War Wagon" (1967) basked in the by-play between John Wayne and Kirk Douglas, and by the time Kennedy made the popular "Support Your Local Sheriff" (1969) and its enjoyable sequel, "Support Your Local Gunfighter" (1971) he had firmly moved into spoof territory.

TV-movies dominated Kennedy's credits from the 70s on; "Kate Bliss and the Ticker Tape Kid" (1978) and "More Wild, Wild West" (1980) are typical of the light touch he brought to the small screen during this period. The broadly handled Hulk Hogan action feature "Suburban Commando" (1991) played up Kennedy's jokey side, but his elegiac TV-saga "Once Upon a Texas Train" (1988), with Willie Nelson as an aging outlaw and Richard Widmark as a former Texas ranger, showed that Kennedy's earlier affectionate sobriety had not left him entirely.