First-half goals from Chris O’Grady and Gevaro Nepomuceno condemned the Shrimps to a fourth defeat of the season on a day when their efforts deserved more.
Jim Bentley’s players enjoyed much the better of the chances at the Globe Arena but were made to pay for a combination of defensive errors, wastefulness in front of goal and good goalkeeping from Oldham’s Daniel Iversen.
Whether he should have been on the pitch for the last quarter was debatable after a confrontation with Jason Oswell but he made the most of his good fortune.
Bentley had made one change from the side that defeated Northampton Town in midweek.
With skipper Barry Roche suspended following his red card, former Blackpool keeper Mark Halstead came in for his debut.
He had a solid enough afternoon between the posts and could do nothing about either of the visitors’ goals.
Both were eminently avoidable from a Morecambe perspective but they were finished clinically - which was the difference on the day.
The Shrimps played the better football but were unable to take advantage of their opportunities, while in contrast, Athletic were less pretty eye but deadlier in front of goal.
Bentley’s players began well but one nice passage of play ended with Zak Mills firing out of the ground while a quick free-kick saw Rhys Oates shoot narrowly off target.
Another direct Oates run ended with him brought down 19 yards out, only for Liam Mandeville to send the free-kick into the massed ranks of travelling supporters.
George Edmundson had two shots blocked by Josef Yarney and Mills before the game turned with two goals in as many minutes.
The first came on 27 minutes as Morecambe failed to deal with a cross and the ball eventually dropped for O’Grady to finish smartly.
It was quickly 2-0 as Mills could only head a cross straight into the air and Nepomuceno emphatically volleyed past Halstead.
Rather than let their heads drop, Morecambe rallied with Iversen keeping out Yarney’s header from Mandeville’s corner.
A better chance fell in first-half added time when Oswell, who had a running battle with the visitors’ defence all afternoon, got behind Edmundson but could only direct his lob off target.
Jose Baxter shot wide for the Latics early in the second half but it was the home side who continued to have more of the attempts on goal.
A rampaging Mills run ended with a shot flashing across goal, Andy Fleming’s volley was blocked and Iversen did excellently to push Mandeville’s shot behind.
The keeper, however, could consider himself lucky to stay on the pitch for the final quarter.
Taking exception to Oswell’s robust challenge, he looked to push his head into the Shrimps’ striker and was perhaps fortunate to only be cautioned.
He celebrated that let-off with a low save from Steve Old’s header before Morecambe almost conceded a third when a goalmouth scramble somehow ended with the ball being cleared.
Both sides rejigged their line-ups as the second half progressed but it was Leitch-Smith who went closest to scoring again, only for Iversen to deny him at point blank range.
A more routine save kept out Aaron Wildig’s deflected effort and Vadaine Oliver failed to convert Kevin Ellison’s header as, despite four minutes of added time, the Shrimps could not fight back.
Morecambe: Halstead, Mills, Old, Yarney, Conlan (Mendes Gomes 89), Mandeville, Fleming, Wildig, Oates (Ellison 79), Leitch-Smith, Oswell (Oliver 72). Subs not used: Sczepaniak, Kenyon, Cranston, Hedley.
Oldham Athletic: Iversen, Hunt, Clarke, Edmundson, Taylor, Branger (Graham 46), Gardner, Missilou (Maouche 84), Nepomuceno, Baxter (Lang 64), O’Grady. Subs not used: De la Paz, Benteke, Stott, Hamer.
Referee: Martin Coy.