Clayton Donaldson scored twice as Brentford extended their unbeaten league run to 13 games at Oldham.
Harry Forrester's cross was headed home by Donaldson from eight yards to give the Bees an early lead.
Matt Smith, Jose Baxter and Cliff Byrne fired wide for Oldham, before Donaldson headed at home keeper Dean Bouzanis.
Brentford were comfortable throughout, but doubled the lead when Sam Saunders released Donaldson to slide home his 17th goal of the season late on.
View from the dressing room
Brentford boss Uwe Rosler told BBC London 94.9:
"We should not look at the table and we must concentrate on our performances.
"It was important that we started winning again."
"Oldham is a very tricky place, they're very hot and cold."
"It was important that we scored the first goal very early."