It was a tale of two halves for Orient at Brisbane Road today, and a result which could mean so much at the end of this long campaign.
Orient now stand in 15th place in League One after this victory over a promotion chasing Oldham led by Latics legend Joe Royle.
The clash also saw the return of striker Adam Boyd after six weeks absence through injury.
His second half appearance saw him play up front with Scott McGleish in what is probably Orient's strongest attacking partnership.
And it cannot have come soon enough for Boyd because he is in danger of having his goal king crown taken by McGleish, after the 35-year-old scored his fifth goal in nine games.
The 35-year-old netted Orient's equaliser from the penalty spot, early in the second. Later in the 84th, Jason Demetriou struck a pearler of a shot which was worthy of winning any game, and did so this one.
Afterwards, O's boss Geraint Williams said: "Oldham came here and made us look like the away side and that's not acceptable.
"So we had a good strong chat about it at half time and set about repairing the damage. We were pleased the lads managed to do that.
"I thought the players reacted magnificently. They did well to get back and then win the game. It's a big three points."
McGleish's strike cancelled out the lead Oldham had taken in the first half through Danny Whitaker.
He put the visitors ahead on 37 minutes with a sweet left footed shot from 25 yards past Jones at full stretch to his right.
It was the sole notable action of a first half which had boss Williams forever bellowing on the edge of his technical area, and ended with fans booing the officials off the field.
Oldham were far superior in the first half. Orient simply did not show up for this battle of the O's.
Lewis Alessandra lifted a lob over Jones' head which left the keeper helpless but went harmlessly over the crossbar, on 20 minutes.
Jones recovered fast when he spilled Sean Gregan's low shot from 18 yards, which came after Reuban Hazzel had won a free kick just outside the Orient area.
The sun came out for the second 45, and the home fans' spirits were soon lifted as it was a different O's side which took to the field. The hosts looked lively and had cutting edge, which soon showed.
Dean Morgan replaced Paul Terry at half time and almost made an instant impact with a low fizzing shot which brushed Oldham keeper's Shane Supple's far post.
Substitute Dean Morgan, on for Paul Terry, won a penalty from a collision with Reuben Hazell 10 minutes after the restart.
On loan Morgan made the most of incident, but it was the climax of a lively cameo down the left flank by the 25-year-old, who had to depart soon after with a knock, to be replaced by JJ Melligan.
Orient continued to put Oldham under the cosh and got their reward in the 84th minute when Demetriou took possession on the edge of the box and struck his shot past the keeper and in off the post.
The win sent the 3,095 fans wild, and Orient, for now, into the promised land of midtable safety.
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