David McGoldrick, on loan from Southampton, and Bjarni Vidarsson, on loan from Everton, both hit the target to condemn promotion hopefuls Oldham to their third straight defeat.
Bournemouth were struck by injuries with former England star Darren Anderton and top-scorer James Hayter the chief casualties, while Oldham had three players ruled out by suspension.
And it was the visitors who displayed a sharper cutting edge to pick up only their second away victory of the season.
Oldham were on top for the first 29 minutes with winger Andy Liddell the focal point of most of their attacks.
Liddell hit a long-range free kick which Bournemouth keeper Neil Moss did well to save before the same two men clashed on 13 minutes and Moss came out on top again.
Oldham midfielder Gary McDonald sent two efforts off target but highly-rated youngster Chris Taylor limped off with an injury.
And Bournemouth went in front with a soft goal as McGoldrick controlled the ball 20 yards out and aimed a shot inside the post as Oldham keeper Alan Blayney was caught unawares.
Two minutes later Bournemouth doubled their lead on the break as McGoldrick played a square ball to Vidarsson, who made headway into the area before finding the bottom corner from 12 yards.
Richie Wellens went close at the other end but Bournemouth full-back Warren Cummings had a chance to make it 3-0.
Oldham replied on the stroke of half-time after Neil Young was guilty of a careless challenge on Chris Porter deep inside the box.
Liddell smashed in the penalty as Moss went the right way but could not keep it out.
There was a great opportunity for Oldham to equalise on 56 minutes but Porter missed the target from only ten yards.
Paul Warne headed wide and Porter was again lacking in accuracy as the home side lost their way.
Oldham went down to ten men in injury-time when debutant defender Ben Turner was shown a straight red card for violent conduct after reacting angrily to a late challenge by Marc Wilson.