In 1957, Provost won the role of Timmy Martin in the CBS television series Lassie. He joined the show at the top of the fourth season as co-star with Tommy Rettig, Jan Clayton, and George Cleveland. Midway through the season, George Cleveland died and Rettig and Clayton departed. The show was revamped to focus on Provost as Timmy. The following year, he met June Lockhart on the set, who would play his mother, Ruth Martin, and would remain close friends. On December 25, 1958, Provost and Lassie were holiday guests on NBC's The Ford Show, Starring Tennessee Ernie Ford.
For seven seasons, 1957–1964, audiences grew to love Timmy and his adventures with Lassie. Timmy's canine companion was played by three dogs that were all descendants of Pal, the original Lassie from the MGM films: Pal's son Lassie Jr. and his grandsons Baby and Spook. In a 2014 interview, Provost said: "I worked with Baby for five years straight. Obviously, he and I really bonded. He was my favorite and I also thought he was the most intelligent of the ones I worked with. They were all great dogs."[1]
In 1964, however, Provost was 14 and chose not to renew his contract, although Campbell's Soup Company, the sponsor, wanted three more years.[2]
In 1994, Provost received a star on the Hollywood Walk of Fame at 7080 Hollywood Blvd. His memoir, Timmy's in the Well: The Jon Provost Story, was released in December 2007 (Cumberland House Publishing, ISBN978-1581826197). In August 2008, Provost was honored with a "Lifetime Achievement Award" at the Pocono Mountains Film Festival.