Best known as the American lead singer of doo wop group The Robins, Chapman joined the doo-wop group in 1952 singing alongside Bobby Nunn, Billy Richards, Roy Richards, Ty Terrell, and later Carl Gardner. During that time, the Robins recorded for RCA, and later Jerry Leiber and Mike Stoller’s Los Angeles -based “Spark” label. In 1955, when Leiber and Stoller took Robins members Nunn and Gardner east to form the Coasters, the Robins recruited H. B. Barnum, and continued recording for the Whippet label. In 1958, he wrote “Sweet Pea” (Class Records #232) for Bob and Earl.
Chapman later became a member of one of the Coasters’ many spin-off groups, The Coasters Mark II, which included Bobby Nunn, Bobby Sheen, and Billy Richards, Jr. In 1977, along with Billy Guy and Jerome Evans, he sang on “Paid The Price” on Michelle Phillips’ album Victim Of Romance. Chapman would also substitute for his brother Carl Gardner a few times in the 1990s and 2000s with The Coasters. He still performed as Grady Chapman & The Robins with various back-up musicians until his death.