Billy Mckay opened the scoring just after the half hour mark, curling home from 12 yards to give Latics the lead.
Five minutes later and it was two for Athletic as Lee Erwin hammered home from the edge of the box.
Athletic dominated the game from start to finish, passed the ball with confidence and energy throughout and go level on points in Group D with opponents Fleetwood Twon
Manager Stephen Robinson named a strong starting line up but it would be the visitors who had the first chance of the game.
Full back Kieran Wallace had space in the area to shoot but his shot was deflected over by Cameron Burgess and from the resulting corner Ashley Eastham just headed over for the Cod Army.
Latics grew into the game, started to dictate possession and had chances to take the lead.
Good work from Mckay saw him feed Carl Winchester, who was making his first start of the season. He prodded the ball into the path of Brian Wilson to strike but he dragged it wide of Chris Neal’s goal.
The next player to go close for Latics was Mckay who shot wide of the goal after Winchester’s low corner into the box.
Athletic were pushing for the opening goal when Erwin dragged a shot wide of the goal from distance before Jamie Reckord and Paul Green found themselves in the referee’s notebook.
Just before the half hour mark, against the run of play, Fleetwood could have found themselves ahead.
Wallace found himself in a lot of space in the penalty area but fluffed his lines in front of goal which was a let off for Latics.
Just after the half hour mark, however, Latics took the lead through a lovely finish from Mckay.
All the work, though, was done by Ryan Flynn who won the ball on the half way line for Latics. He raced 40 yards and laid it on a plate for Mckay who curled into the bottom corner from 12 yards.
The Northern Irish international almost made it two minutes later as he met a cross into the box from Wilson but he smashed the post from close range.
However, on 38 minutes, Latics did make that pressure pay as they went two goals ahead.
And what a goal it was from Leeds loanee Erwin. The striker picked the ball out the air with his foot, cut inside on his right foot and hit a sumptuous effort into the bottom corner leaving Neal with no chance.
Winchester was at the heart of the action for Latics as he created a chance for Mckay before the break but also had his own chance, firing over from 18 yards after a good flowing move.
Latics started the second half much as they finished the first, dominating possession and creating chances.
The first chance of the second half came on 48 minutes as Green played the ball through to Flynn who laid it into the path of Erwin to strike but it went inches past the post.
Erwin again had two half chances, twice firing wide of Neal’s goal from outside the box.
Latics were knocking the ball around with good energy and confidence and won a corner on 55 minutes after a passing move which went into double figures.
From the resulting corner, Winchester’s drilled set piece found the head of the onrushing Burgess but the defender’s header rebounded off the post and away from danger.
Athletic were piling on the pressure and Winchester headed over just before the hour mark after a great delivery into the box from Flynn.
Two chances in a minute followed as firstly Winchester’s corner found Burgess at the back post and his header rolled along the line before being cleared, whilst 30 seconds later, Flynn forced a smart save from the Fleetwood goalkeeper.
Robinson made three changes bringing on Lee Croft, Ollie Banks and Freddie Ladapo in place of goalscorer Mckay, Green and Winchester, all three earned a standing ovation.
Fleetwood were not troubling Connor Ripley’s goal as Latics were in complete control of the game.
Latics passed, and passed, and passed in the final minutes of the game, seeing the game out professionally and going level on points with Fleetwood in Group B of the Checkatrade Trophy.
Fleetwood Town: Neal, Jonsson (Glendon 63’), Eastham, Ball (Cole 32’), Grant (Hunter 46’), Bolger, Wallace, Neirennold, Duckworth, Woolford, Jakubiak.
Subs not used: Cairns, Davis, Roberts, Sowerby.
Oldham Athletic: Ripley, Wilson, Burgess, Clarke, Reckord, Fane, Winchester (Croft 73’), Green (Banks 73’), Flynn, Erwin, Mckay (Ladapo 77’).
Subs not used: Kettings, Law, Klok, Osei.
Goals: Fleetwood Town 0-2 Oldham Athletic (Mckay 32’, Erwin 38’)