Charlie MacDonald had the ball in the net in the fifth minute for the Londoners but it was ruled out for a foul on Scott Wootton. Two minutes later Brentford did go ahead from the penalty spot after Aaron Cresswell handled a Craig Woodman cross. Kevin O’Connor fired low into the corner of the net.
O’Connor scored his second with a free-kick from long range in the second half and Marcus Bean put the icing on the cake with a third goal.
After O’Connor had opened the scoring from the spot, Dale Jennings twice missed the target as Tranmere tried in vain to get back on terms before the break.
It needed a good save by Bees keeper Ben Hamer to turn aside an Enoch Showunmi effort for the home side approaching the hour-mark. Then Lucas Akins just missed the target from long range.
The Merseysiders were rocked by a second Brentford goal after 66 minutes. A free-kick by O’Connor from fully 35 yards found it’s way through a pack of players and sneaked just inside the far post. And Bean made it three in the 81st minute from a low cross by MacDonald to complete a miserable afternoon for the home side.