Everton players celebrating
Everton brought League One Oldham's FA Cup run to an end as the Premier League side showed their superiority to earn a last-eight tie against Wigan.
Kevin Mirallas guided in Darron Gibson's cross to put Everton ahead.
The hosts had two scares when Jose Baxter hit the post and Gibson handled in his own area, but Leighton Baines later converted from the spot, reports the BBC.
Leon Osman nodded in Steven Pienaar's cross and despite a towering header from Matt Smith, Oldham fell short.
Having beaten Liverpool in the fourth round, and earned the replay with Everton via a stoppage-time Smith header earlier this month, the Latics could not contain opponents who sit 58 places above them in the league ladder.
Victory for Everton came as a result of more incisive attacking play in the final third and it ended a sticky period as they claimed their first win in five league and cup games.
It keeps manager David Moyes's quest for a first trophy in his 11 years at the club alive, having guided Everton to last year's semi-finals and the final in 2009.
Contrastingly for Oldham caretaker boss Tony Philliskirk, this was his first defeat during his five-game period in charge.
Although there are uncertainties surrounding Moyes's position as he delays a decision about his future until the end of the season, this was a display which could further help Philliskirk's cause to make his position permanent.