Grayson had to change his line up with Bailey Wright being injured so Jack King came in to deputise at the back. Apart from that Preston lined up in their usual 4-4-2 formation.
Preston started brightly and were ahead not long into the game thanks to Humphrey. The winger cut in from the right and shot low with his left foot. There is some debate as to who got the final touch with acting skipper Keane claiming he got a touch.
The visitors controlled much of the game but had to wait until the second half before doubling the lead. Humphrey made an excellent run down the right beating his man before slotting a cross for Garner to finish.
Oldham then got back into the game with a superb left foot volley that Rudd had no chance of saving and it looked like Preston's lead might be under threat for the final part of the game.
Soon after the game change again in Preston's favour. Garner's header was handled by Harris-Clarke ont he line with the Oldham player sent off. Garner struck the penalty at a height where the keeper managed to get a hand and push the shot away.
Despite the disappointment of the penatly Garner notched his second with a shot from outside the box rebounding off one post onto the othe before rolling in. Preston were comfortable to the finish.
The gap on second place closed to four points with Brentford and Orient facing each other on Saturday. Before then Preston travel to Stevenage on Tuesday night for another important game in the run in.