As a child, Rist played Cousin Oliver in the final six episodes of The Brady Bunch. With the regular children all getting older, his inclusion was intended to reintroduce cute younger children to the series. With his Dutch Boy haircut and wire-rimmed glasses, his resemblance to pop singer John Denver and juvenile appeal, he seemed ideal; however the plan became moot as the network had opted to not renew the series before his debut anyway. This gave rise to the term "Cousin Oliver Syndrome". Rist's character, Oliver, uttered the final line of the final episode.
After The Brady Bunch he co-starred in a Saturday morning show called Big John, Little John, was Glendon Farrell on the David Hartman vehicle Lucas Tanner, and in 1976 and 1977 played Ted Baxter's son David on The Mary Tyler Moore Show. In 1980, Rist played "Dr. Zee" on Galactica 1980. He made four guest appearances on CHiPs and the short-lived CBS series Whiz Kids, and also played Booger in a failed Revenge of the Nerds TV pilot. In 1986, Rist had a notable supporting role as Milo in the action film, Iron Eagle which was a box-office hit despite being critically panned.
As an adult, Rist has worked as a voice actor, such as in the Teenage Mutant Ninja Turtles film series (as the voice of Michaelangelo); from 1984 to 1986, he starred in the Saturday morning cartoon Kidd Video, playing the character Whiz both in live-action music videos and animated sequences. He was the voice of Star, a Siberian husky, in the 1995 Universal Studios film Balto. He was also the voice of Aaron in the PC game Star Warped. An episode of Batman: The Animated Series titled "Baby Doll" contained a character called Cousin Spunky that was intended to boost sagging ratings of the fictional Baby Doll sitcom, a clear reference to Cousin Oliver (Rist lent his voice to the episode, but did not play Cousin Spunky; his character was an adult).
Rist also voices characters Choji Akimichi from Naruto, Itsuki "Iggy" Takeuchi from Initial D and Bud Bison from Megaman Starforce.
Robbie Rist is currently the voice of Stuffy, Doc's overly proud stuffed dragon, in Disney Junior's new animated series Doc McStuffins.
Recently, he voiced Griffin in Terminator Salvation, he also recently provided additional voices in Final Fantasy XIII, as well as reprising his role as Michelangelo in a fan-made movie about Casey Jones.