Clydebank avenged two earlier defeats by beating Berwick far easier than the 2-1 scoreline suggests.
Despite conceding a goal after 60 seconds when Gary Wood netted the rebound after Derek Wylie saved his penalty, the Bankies took control.
Martin Glancy, who had earlier hit the post, equalised after Clydebank forced four successive corners.
Glancy also played a major part in setting up the winner in 72 minutes. He was brought down by Alan Neill and Eric Paton thumped home the penalty.
A hugely disappointing Berwick failed to force a single corner.
Scott Murdoch of Clydebank and Kevin Magee of Berwick were booked.