Beastie Boys was never formed.
Ad-Rock . He is best known as a member of the hip hop group the Beastie Boys . Adam Yauch . He was best known as a founding member of the hip hop group Beastie Boys . Beastie Boys . For the majority of their career , the group consisted of Michael `` Mike D '' Diamond ( vocals , drums ) , Adam `` MCA '' Yauch ( vocals , bass ) and Adam `` Ad-Rock '' Horovitz ( vocals , guitar ) .