He started out in Junior "B" with the Bruins' farm team the Lakeshore Bruins in Toronto. He then played Junior "A" with the Barrie Flyers. Brooks had a long minor league career which included seven seasons for the Providence Reds of the American Hockey League, and shared the award for lowest goals against average in the AHL in 1972. In the 1972 season, however, the Bruins, who owned his rights, lost several goaltenders; top prospect Dan Bouchard to expansion, star Gerry Cheevers to the WHA and veteran Eddie Johnston to a trade with the Toronto Maple Leafs. This opened the door to Brooks' recall as the backup goaltender.