Born in Illinois, one of Johnston's first gigs was as a member of the surf band the Gamblers before becoming a staff producer at Columbia Records. In 1965, he joined the Beach Boys for live performances, initially filling in for the group's co-founder Brian Wilson. Johnston's first appearance on the band's records was as a vocalist on "California Girls" (1965). He later contributed original material to the group's albums, including "The Nearest Faraway Place" on "20/20" (1969), "Tears in the Morning" and "Deirdre" on "Sunflower" (1970), and "Disney Girls (1957)" on "Surf's Up" (1971).