On-loan strikers Lee Barnard and Chris Iwelumo were both on target for the Latics, who hope to name Paul Dickov's replacement before facing Everton in the FA Cup fifth round next weekend.
Under caretaker boss Tony Philliskirk, they went ahead after 22 minutes at Boundary Park when a mistake by visiting captain Dean Lewington allowed Lee Croft to find Barnard and he fired inside the far post from eight yards out.
Jordan Obita almost doubled the lead with a deflected effort but the Dons levelled after 39 minutes when Daniel Powell chased Jon Otsemobor's long pass and drilled home a fine shot from an angle.
Oldham were back in front just before half-time as Jean Yves M'voto met Jose Baxter's right-wing free-kick with a powerful 10-yard header.
And it was 3-1 after 53 minutes when the Dons defence failed to clear Obita's cross and Iwelumo slammed in the loose ball from close range.
Both teams missed good chances - Iwelumo for Oldham and Izale McLeod at the other end - before the home side completed a much-needed win.
The Dons, however, have now suffered three straight defeats and find themselves in the bottom half of the League One table.
