The promotion-chasing Dons – who beat Oldham 7-0 in the reverse fixture before Christmas – returned to form with a slick display against injury-hit opponents.
They should have struck early when Latics goalkeeper Jake Kean spilled a shot from Dean Bowditch and Will Grigg fired the rebound against a post.
Kean made amends with a save from Grigg’s volley, but the visitors went ahead on 25 minutes when Samir Carruthers set up Bowditch for a smart 12-yard finish into the far corner.
Oldham almost levelled after Carl Winchester’s brilliant pass found Jonathan Forte, who was denied by onrushing keeper David Martin.
Instead the Dons doubled their lead on 37 minutes as Carruthers crossed from the left and Daniel Powell slotted in from close range.
Oldham’s Conor Wilkinson hit the woodwork, only for Ben Reeves to make it 3-0 in the 65th minute with an unstoppable 20-yard shot into the top corner.
The home side bagged a consolation 10 minutes from time as Rhys Turner burst through the Dons defence to score from 10 yards.