Swindon manager Mark Cooper felt Oldham's desire to win was greater than that of his Town team after seeing the Robins lose 1-0.
Jonathan Grounds hit a 73rd-minute winner to give the Latics a deserved 1-0 victory.
The left wing-back finished off a neat move initiated by the influential Gary Harkins. He set up substitute Jon Stead, who joined the Latics in a last-minute January transfer window move, but his shot was blocked and Grounds fired home the rebound.
It was Oldham's first away win since late November and dented the play-off hopes of out-of-sorts Swindon, who finished the match with 10 men after half-time sub Troy Archibald-Henville was dismissed late on for a second yellow card offence.
"I could put the conditions up as an excuse. It wasn't a pretty day for football, but the difference between the teams was that they wanted it a little bit more than we did," said Cooper.
"It was a disappointing performance by us. Whether we had next week's Johnstone's Paint Trophy semi-final tie at Peterborough on our minds, I don't know.
"But we're just outside the play-offs, so league points are vitally important, especially when you are playing at home."
Cooper felt that one of the few positives that came from Swindon's performance was that of Archibald-Henville.
"I thought he was outstanding when he came on - and now he'll be suspended," said Cooper.
"We wanted to give him pitch time and he did really well after replacing Darren Ward."