In 1970, Brewster, with his brother Rick Brewster and Doc Neeson, formed Moonshine Jug & String Band in Adelaide, the band evolved into The Keystone Angels in 1973.
[2] An appearance at the 1975 Sunbury Pop Festival, resulted in touring with AC/DC, and with Chuck Berry as his backing band.
Brewster left the band and joined The Party Boys in February 1986.
[2] He remained with The Party Boys until mid-1989, before teaming up with his friend, Alan Lancaster to form The Bombers.
John was inducted into the SA Music Hall of Fame on 16 May 2014 alongside his brother Rick, Redgum's John Schumann and Rose Tattoo's Rockin' Rob Riley.