By 1973, Lassie was well established in syndication after a long run on CBS. Believing that the iconic collie could still draw viewers on network television, Filmation acquired a license to produce a Saturday morning series. Lassie's Rescue Rangers, however, lasted just 1 season as a Saturday series, and was moved to Sundays the next year. The pilot, "The Spirit of Thunder Mountain", aired as an installment of ABC's Saturday Superstar Movie. Here's the open, uploaded by Avatar3700 to YouTube, to Lassie's Rescue Rangers:
I remember watching this show as a 10 year old, and, yes, I also watched the live-action Lassie from time to time. Rescue Rangers marked the last Filmation work of Emmy winner Ted Knight (The Mary Tyler Moore Show), who also served as narrator for Hanna-Barbera's Super Friends, the centerpiece of ABC's 1973 Saturday morning lineup. With the original Lassie now on RTV (check local listings), and with RTV carrying a number of Filmation series, it's a matter of time before the Rescue Rangers ride again.