In 1960, he began an 11-year run as Robbie Douglas in the show "My Three Sons" starring Fred MacMurray. Initially airing on ABC, the show moved to CBS in 1965. During production of "My Three Sons", Grady both appeared with his own band The Greefs on the series, writing two original songs for the show ( "A Good Man To Have Around The House" & "Leaving It Up To You") and was the drummer for The Yellow Balloon, whose self-titled song became a minor hit in 1967. For a while during the run of the series, he attended Los Angeles City College.