He joined the Ontario Educational Communications Authority (later TVOntario) in the early 1970s as a manager and, in 1974, was assisting with the establishment of its regional councils, when he was told OECA had acquired the broadcast rights to three Ingmar Bergman films and was asked if he had any ideas on how the station could air them in an educational context. Yost packaged the shows as Three Films in Search of God adding educational content in the form of interviews, introductions, and discussions thus creating the model for what became Saturday Night at the Movies, which became the channel's longest-running, and one of its most popular shows. Yost also developed Magic Shadows, which showed classic serials in half-hour early evening installments with introductions providing background and interesting details by Yost, the movie review show Rough Cuts, Talking Film and The Moviemakers. In 1979 he appeared in Ida Makes a Movie, the first of four television shorts that spawned The Kids of Degrassi Street in 1982.