Latics lost out to Scunthorpe who earned a 2 - nil victory at Boundary Park.
Abo Eisa and Matthew Lund were the scorers for the opposition.
Eisa netted for the seventh time this season in the 35th minute, cutting in from the left flank and unleashing a superb 25-yard shot that arrowed its way into the far corner.
Lund sealed victory in the 83rd minute when a Ryan Colclough corner kick was deflected into his path, controlling and firing a back-post shot that carried enough power to get beyond Oldham goalkeeper Zeus De La Paz.
Scunthorpe were comfortably the better side throughout with Eisa rifling home the opener 10 minutes before the break.
John McAtee went close to doubling his side's advantage in the 51st minute when volleying narrowly wide from 10 yards.
Oldham failed to muster a shot on target until half-time substitute Mohammed Maouche warmed the palms of goalkeeper Jake Eastwood with an effort from 20 yards out after 53 minutes.
Dina Maamria's hosts improved after the interval but lacked a cutting edge, before Lund made sure that the visitors ended their run of back-to-back defeats in positive fashion.
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