Oumare Tounkara opened the scoring, calmly slotting home a one-on-one five minutes before half-time, and Filipe Morais came off the bench to claim his first goal for Latics.
His strike proved crucial as fellow substitute Robbie Simpson pulled one back for the Bees.
"We got what we deserved - in fact we got more than we deserved because we scored a goal," he said.
"The performance was nowhere near. We knew all about Oldham's energy and enthusiasm but we didn't cope with it and we gave the ball away too cheaply.
"There were just too many glaring errors and it's annoying when you work hard on things all week but don't do them on a Saturday."
Source: PA
Source: PA