Which song was the Osmonds' first U.S. number-one single?

The Osmonds are an American family music group who reached the height of their fame in the early to mid- 1970s. Currently consisting of a duo of original members Merrill Osmond and Jay Osmond, the group had its best-known configurations as a quartet (billed as the Osmond Brothers) and a quintet (as the Osmonds). The Osmond Brothers began as a barbershop quartet consisting of brothers Alan, Wayne, Merrill and Jay. They were later joined by younger siblings Donny and Jimmy, both of whom enjoyed success as solo artists.

Record producer Mike Curb saw the Osmonds perform as a band and recognized that they combined a rare mix of polished performing style, instrumental skill, and vocal talent. He signed the Osmonds to MGM Records and arranged for them to record at Muscle Shoals with R&B producer Rick Hall. Under Hall's guidance, the Osmonds hit the top spot on the pop chart with "One Bad Apple" in 1971. The result was their first number-one hit.