Oldham are scrapping for survival but Grayson holds an impressive home record with North End having not lost a home league game since his arrival earlier int he year.
Grayson kept with the formation that played in the second half on Saturday. The 4-3-2-1 formation saw Welsh back int he side for the injured Holmes as Beavon and Wroe supported King.
Preston were poor int he first half and despite having some possession failed to do anything of any note. The visitors looked to break everything up and were competitive.
On another night against better opposition Preston might have going into the break by at least a gola down. Oldham could not force home the ineptness of the home side and Rudd managed to keep out anything on target.
North End started a lot more brightly in the second half. King had a header hit the bar and then Preston were awarded their first home penalty in over a year much to the amazement of the home crowd.
Monakana had come on as a sub and his cross was handled in the box. Wroe converted the penalty to give Preston the lead and the visitors then had to come out and play more leaving gaps at the back.
Preston capitalised ins toppage time when the Oldham keeper came up for the corner. The ball was cleared and Hayhurst beat the last defender. He almost stumbled as he ran into the opposition half before playing the ball into the gaping net.
Grayson will now look to build ont his home success with the final home game at Tranmere to come in ten days time. If he can get the away form up to a similar level then Preston may well enjoy a fruitful season next year.