Oldham put on a four-star display to cruise into the second round of the Carling Cup at Mansfield's expense.
The League One side were comfortable throughout, taking the lead on 20 minutes through Neil Kilkenny's strike.
Jean-Paul Kalala then followed up a parried Craig Davies shot to double the lead, before John Mullins's header reduced the deficit for the visitors.
However, Oldham put the game out of reach when Deane Smalley and Davies scored inside the last eight minutes.
Oldham: Crossley, Eardley, Thompson, Gregan, Giddings, Liddell, Kalala (Taylor 71), Allott, Kilkenny (McDonald 86), Davies, Ricketts (Smalley 80).
Subs Not Used: Bell, Wolfenden.
Goals: Kilkenny 20, Kalala 27, Smalley 82, Davies 86.
Mansfield: Muggleton, Mullins, Martin McIntosh, Buxton, Jelleyman, Arnold, Bell, Dawson, Martin (Sleath 60), McAliskey (Rory Boulding 60), Michael Boulding.
Subs Not Used: White, Wood, Reet.
Booked: Jelleyman, McAliskey, Martin McIntosh.
Goals: Mullins 72.
Ref: S Bratt (W Midlands).