Oldham produced a convincing display to end Chasetown's FA Cup dreams and earn a second round tie against Brentford.
Chasetown held out for half an hour before Paul Warne's fired a 20 yard shot high into the net.
Chris Porter made it 2-0 from close range after good work from Andy Liddell and added his second and Oldham's third with a shot from the edge of the box.
Chris Hall headed home the Latics' fourth late on with Paul Edwards the provider with the cross.
Oldham: Day, Forbes, Daniel Hall, Owen, Edwards, Warne, Hughes, Wellens (Eyres 82), Butcher, Porter, Liddell (Chris Hall 79).
Subs Not Used: Cronin, Haining, Beckett.
Booked: Butcher, Chris Hall, Hughes.
Goals: Warne 31, Porter 56, 75, Chris Hall 84.
Chasetown: Bryan, Slater, Thompson, Steven Edwards, Aulton (Bytheway 45), Harris (Turner 67), Harrison, Horler, Damien Whitcombe (Huckfield 83), Bullimore, Karl Edwards.
Subs Not Used: Smith, Taylor.
Ref: C Boyeson (E Yorkshire).