Towering striker Matt Smith was Oldham's FA Cup hero once again as his last-gasp equaliser earned the npower League One strugglers a fifth-round replay with Everton.
Smith produced an all-action display to score twice in Latics' round four triumph over Liverpool but had been sidelined since with a shoulder injury sustained in the match.
But the 23-year-old Manchester University business management graduate, who Oldham plucked from non-league obscurity at Solihull Moors, climbed off the bench to head home Jonathan Grounds' corner in the fourth and final frantic minute of stoppage time.
As was the case against Liverpool, Latics - playing under caretaker manager Tony Philliskirk - had their Merseyside opponents reeling when on-loan Reading winger Jordan Obita gave them a 13th-minute lead.
Goals from Victor Anichebe and Phil Jagielka either side of half-time put David Moyes' men in the driving seat but Everton goalkeeper Tim Howard was forced to save well from Smith and Robbie Simpson.
Howard was finally beaten as Smith prospered in a crowded penalty area that featured Latics keeper Dean Bouzanis attacking Grounds' decisive delivery.
Oldham caught Liverpool cold with an early goal in their round four triumph but were unable to repeat the trick during a fragmented opening.
Nikica Jelavic, restored to the Everton starting line-up in favour of Kevin Mirallas, had a glimmer of an opening in the eighth minute from Steven Pienaar's through ball but the Croatia striker was crowded out by Latics centre-back James Tarkowski as he looked to get a shot away.
Former Everton youngster Jose Baxter pulled back the advancing Pienaar to present Leighton Baines with an inviting free-kick opportunity.
The England left-back's strike was deflected over and, after Oldham dealt with the resulting set-piece pressure, Boundary Park was sent into raptures.
Lee Croft broke unchallenged from his own half down the Everton left before driving low across goal where Obita's perfectly-timed run was rewarded with a tap-in.
The lead remained intact for 11 minutes until Everton successfully took a direct rout to goal.
Jagielka's raking long ball was flicked on by Jelavic and Anichebe got the better of Jean-Yves Mvoto to rifle past Bouzanis.
Undeterred, Oldham surged forward in response and, after veteran striker Chris Iwelumo made his presence felt to cause havoc inside the Everton area, Obita thudded a shot against the base of the post.
In the 32nd minute, Jelavic came out on the wrong side of a marginal offside call when he converted Pienaar's defence-splitting pass.
A lucky break would have been welcome for Jelavic and the heavy touch that allowed Bouzanis to mop up further danger shortly before the interval displayed the dwindling confidence of man with one goal in his last 12 outings.
He had a new partner in attack for the second period as Mirallas replaced hamstring victim Anichebe and the new man would make an instant impact in the 48th minute.
Mirallas' in-swinging corner from the left caught out Bouzanis, allowing Jagielka to steal in front and nod into an unguarded net.
Everton were intent on driving home their advantage and some deft interplay between Pienaar and Marouane Fellaini saw the former bring Bouzanis into the action once more.
Another Mirallas corner had Oldham in trouble before the hour, arching past the massed ranks at the near post and narrowly evading Leon Osman.
Philliskirk responded by sending on Oldham's fourth round hero Smith for Iwelumo and club captain Dean Furman in place of James Wesolowski, and the latter visibly sought to rouse his team-mates. Baxter responded by smashing a 25-yard half-volley over.
Pienaar ended an enterprising evening's work by slowly making way for Bryan Oviedo and such Everton gamesmanship was justified as Oldham pressed once more, Tim Howard plunging to his right to superbly deny Smith following a lay-off from fellow sub Simpson.
At the other end Jelavic passed up the opportunity to make the tie safe with eight minutes to play, blazing over from Darron Gibson's fine flighted pass.
In the 89th minute Simpson had a glorious chance to earn a replay as he shrugged off the attentions of Phil Neville to collect Tarkowski's wonderfully-weighted lofted pass, but Howard stopped a shot that lacked purchase before seeing the rebound lashed into the side netting.
Much to Simpson's relief and the locals' delight, Smith would sensationally spare his blushes.