Harvey Saunders scored the only goal as Latics suffered defeat at Bristol Rovers on Tuesday night.
It was a hugely disappointing 90 minutes for the visitors as they struggled for large parts and were unable to make a meaningful impression on the game.
While a change in shape and personnel at half-time brought some improvement in the second period, this was poor all-round performance from Latics and leaves them still looking for their first points of the campaign.
Although Head Coach Keith Curle remained absent a week after receiving a positive Covid-19 test, Latics were able to hand a first competitive start to Hallam Hope following his time on the sidelines due to the virus.
With Danny Roberts injured, Laurie Walker played in goal after re-joining the club on an emergency loan from MK Dons, while Dylan Fage returned at wing-back.
The only goal arrived nine minutes before half-time, Saunders finding space inside the box to head in a left-wing cross from Harry Anderson and it was a goal that Rovers deserved.
The pressure from Joey Barton’s side had been mounting as the first period went on and Latics would probably consider themselves fortunate not to have been further behind at the interval.
The visitors had actually made a reasonable start, breaking quickly in the 16th minute as Callum Whelan played the ball out to Fage, whose ball into the box was held by goalkeeper James Belshaw.
But Latics were unable to mount any serious pressure and as the half progressed it became one-way traffic in favour of the home side.
Saunders headed wide from inside the area, before Harry Anderson lifted a shot over and Carl Piergianni was called upon to make a timely block to deny the Rovers wide man.
Dylan Bahamboula sent a dipping free-kick over the crossbar midway through the half but that was only a brief moment of encouragement for the visitors as Luke Thomas flashed a shot across the face of goal.
The home side took the lead through Saunders, before Walker, returning to Latics after two months on loan last season, made two good saves to deny Collins as half-time approached.
A double substitution at the break and a change in formation helped bring about some improvement for Latics but genuine chances were still in short supply.
A free-kick from Whelan reached Ouss Cisse at the far post but his shot was deflected wide, while a header from Jacob Blyth went over the bar.
The best chance for Latics came when Hallam Hope switched play after picking out the run of Nicky Adams, but he blazed his shot over when a composed finish was needed.
Bahamboula also brought a save from Belshaw in the closing stages but there way to be no way back for Latics on a poor evening all round.
Oldham Athletic: Walker, Clarke, Hart, Cisse, Piergianni, Whelan, Hope, Keillor-Dunn (Adams 65), Fage (Diarra 46), Stobbs (Blyth 46), Bahamboula.
Subs not used: Danielewicz, Luamba, Vaughan, Sheehan.
Bristol Rovers: Belshaw, Hughes, Grant, Finley, Thomas (Nicholson 60), Collins, Anderton, Anderson (Harries 76), Saunders (Pitman 76), Baldwin, Rodman.
Subs not used: Ward, Kilgour, Hargreaves, Liddle.
Referee: Sam Purkiss
Attendance: 6,005 (286 away)