It was a comfortable win for Latics over mid-table Bradford, leaving Oldham in 14th in League Two.
All three of the goals came in the first half, as Zak Dearnley, Jonny Smith and Mohammed Maouche found the net before the break.
Kick off had to be delayed at Boundary Park, as an advertising board became partly dislodged and had to be removed.
Dearnley took advantage of a defensive slip in the Bantam's defence, as Anthony O'Connor lost his footing and sent the Latics' man through on a one-on-one. He slotted home for his first goal of his second spell at Boundary Park.
Ten minutes later, Smith doubled the lead as he started and finished a decisive counter-attack - as he picked out the bottom corner from the edge of the box.
On the stroke of half time, Maouche slotted the ball through the goalkeeper's legs from a tight angle to complete a perfect first 45 minutes.
The visitors came into the match a little more in the second period, but the game was done and dusted - with Oldham never showing any signs of giving up their lead.
In fact, it was Latics who almost extended their lead further: Gevaro Nepomuceno tried to pick out Danny Rowe, but the ball ran through to Richard O'Donnell in the Bradford goal.
A double-save from O'Donnell kept the score at 3-0, as both Smith and Nepomuceno tried to slot the ball home, while David Wheater also had a diving header cleared off the line.
It was the first back-to-back wins for Latics since Boxing Day.
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