After trailing 14-6 with 25 minutes to play the Broncos piled on five tries in 21 minutes to overpower a Canterbury side which showed plenty of fight at the end of a horror week.
A scare for the home side early with forward leader Payne Haas forced from the field with a shoulder problem in the eighth minute but he was able to return midway through the half after treatment and went on to play a starring role.