Grayson brought back Joe Garner to partner Kevin Davies up front but otherwise the side remained settled from their draw at Crawley the previous Saturday.
Despite losing their manager Brentford were a well drilled and organised outfit who have been playing consistently as a unit over the past 18 months or so.
The game was fairly even with minimal opportunities until Declan Rudd had a rush of blood to the head in the first half. Donaldson was chasing what seemed like a lost cause with the ball heading out. For some reas Rudd raced to the edge of the box and clipped the striker who went down. Forshaw converted the penalty.
It then set the tone for a mad few minutes as Preston failed to clear the ball. Rudd parried but the ball was played to Trotta who slotted home to double the advantage for the visitors.
Welsh had a free kick blocked by the wall before the break but Preston had little else to show against a hard working if unspectacular visiting side.
Changes were made at the break with Holmes and Kilkenny replacing Brownhill and Keane. The width gave Pretson more attacking options and they started the second half positively.
Preston were awarded a penalty after there was a push in the box. Garner drove the spot kick straight at the keeper and this was probably the turning point as if Preston had reduced the lead they looked like scoring again.
North End had a large spell of possession with chances ina and around the missed penalty but couldn't convert despite the pressure. As they piled forward gaps were left at the back.
Brentfors scored the third after Laird slipped allowing Saunders to finish sublimely in the box. Brentford had not put a foot wrong all afternoon but on another day Preston may have made more of the game.
There were some poor performances out there with Humphrey uncomfortable on the left in the second half being one of them. Garner will rue the missed penalty but Preston must now push on and go on another run over the festive period.