An injury-time goal from defender Jean-Yves M'Voto condemned Reds to a harsh defeat at Boundary Park which brought our play-off challenge to an end.
Mark Connolly had equalised from close range with 13 minutes to go after Matt Smith had put the home side in front but Oldham pinched the points right at the death.
An injury to Connor Essam meant a return in central defence for Connolly after three games out as Richie Barker made one change to the side which had beaten Coventry City a week earlier. Oldham, looking for the point that would guarantee their survival, were unchanged.
A pitch watered extensively before kick off looked in decent condition as the game got underway in Spring sunshine but despite the rise in temperature the game took an awful long time to warm up.
Oldham created their only chance of the half on 17 minutes when Smith found space at the far post to get onto the end of David Mellor's diagonal into the box but he failed to keep his header on target.
Reds immediately won two corners which came to nothing but as the half progressed the visitors began to ask questions of a jittery Oldham defence.
Home goalkeeper Dean Bouzanis twice caused consternation among the Latics' faithful with a couple of wayward clearances but on 33 minutes he came to Oldham's rescue after Paul Hayes had worked a good one-two with Billy Clarke.
Top scorer Clarke bore down on goal from an angle but Bouzanis beat his shot away at the near post. From the corner David Hunt worked a nice move with Clarke whose low ball into the box was nipped off the toes of Joe Walsh by a defender as he arrived in the box to try and make contact.
Apart from a long-range effort by Lee Barnard last seen heading in the direction of Saddleworth Moor that was about it in terms of goalmouth action in an uninspiring first half.
The second period was much livelier and Reds began it strongly with Clarke inches away with a drive from 25 yards on 47 minutes. Bouzanis then plunged to his right to save on the line after a corner from Adams was headed back towards his own goal by Jonathan Grounds.
Little had been seen of the Oldham attack up until then but they took the lead on 57 minutes. SMITH ran at a retreating defence and then hit a powerful left-foot shot from 20 yards which arrowed into the bottom corner, although Paul Jones did get a hand to it.
The boss responded by making a triple substitution with Matt Sparrow, Josh Simpson and Jamie Proctor all coming on and with 13 minutes to a spell of Reds' pressure paid off with an equaliser. Simpson and Mat Sadler worked a corner routine, Adams crossed to the back post and CONNOLLY had the easiest of headers on the line to make it 1-1.
At that stage it looked as if Reds might go on to win it. Proctor nearly profited after another wayward clearance by Bouzanis but with an open goal to aim at he could only drag his shot wide.
But deep into stoppage time Lee Croft swung over a free kick from wide on the left and Jean-Yves M'VOTO climbed at the far post to head home from close range, sparking a pitch invasion from both ends of the ground.
Order was quickly restored but there wasn't enough time for Reds to find an equaliser.