Kenny Dalglish's team seized it, albeit belatedly and with a scoreline that flattered, but the night was scarred by allegations of racist abuse towards the Oldham defender Tom Adeyemi following an altercation with a spectator at the front of the Kop.
The dreadful end to an enthralling Cup tie could not have been more deflating for Adeyemi, the on-loan defender from Norwich who had enjoyed a fine game, for Oldham, who deserved more than what appears a rout but in reality was not, and for the Liverpool team.
Their nerves were tested when Robbie Simpson swept the League One side into a merited lead but Liverpool eventually eased into round four. A fine finish from substitute Andy Carroll, a first goal for the club for Stewart Downing and an outstanding display from Craig Bellamy added to the positives. Ultimately, however, they were overshadowed.
Dalglish, who was unable to comment on the Adeyemi allegations, said: "The scoreline is a bit flattering really. Oldham did their club and manager proud. There were a lot of positives to come out of the game with Stewart, big Andy, Jonjo Shelvey and Stevie [Gerrard] scoring but the result doesn't reflect the distance between the two clubs on that performance."
Before kick-off Liverpool paid a moving tribute to their former defender Gary Ablett, who died on New Year's Day after a long illness aged only 46. Applause for a man respected on both sides of the Merseyside divide commenced long before the referee, Neil Swarbrick, blew his whistle and his name was chanted long and loud by the Kop as Ablett's wife and children looked on from the Main Stand.
Out on the field, Gerrard took his place in a Liverpool starting lineup for the first time since October and his presence served as a reminder not only of his heroics in bringing the FA Cup back to Anfield in 2006 but the club's lamentable record in the competition since that remarkable final against West Ham United. Liverpool have landed some unfortunate draws in the intervening period admittedly, falling to Arsenal and Manchester United at the third-round stage, the latter marking Dalglish's return as manager one year ago, but the fact remains they had won only three FA Cup ties since Cardiff - against Luton Town, Havant & Waterlooville and Preston North End. The furthest Liverpool have gone since lifting the trophy was the fifth round in 2008, and that ended in an embarrassing home defeat to Barnsley.
Their early exchanges against Oldham did not bode well for an immediate improvement as Paul Dickov's side took the game to Liverpool and created the clearer first half chances against a creaking home defence. Shefki Kuqi, Adeyemi and Chris Taylor all went close before Dean Furman slipped a pass into Simpson 25 yards from goal. His first touch sent the ball up, no Liverpool defender came near, and the on-loan striker from Huddersfield Town volleyed superbly beyond José Reina with his left foot.
Simpson raced the length of the pitch after scoring but Liverpool's response arrived before Oldham's wild celebrations had ceased. It was fortunate in the extreme. Shelvey was the architect as he cut inside from the right and shot left-footed at Alex Cisak. The Oldham goalkeeper had it covered until the ball struck Bellamy on the chest and deflected into the unguarded side of his goal.
With parity came a much-improved display from Dalglish's team and they quickly redressed the imbalance in chances created. Gerrard converted a controversial penalty on the stroke of half-time after Adeyemi was adjudged to have pushed Maxi Rodríguez in the back as they challenged for a cross.
"That was a joke," said Dickov, who lamented the ease with which Bellamy was allowed to tee up Shelvey for the third. Carroll came off the bench late on to convert an emphatic left-foot finish from 20 yards before Downing ended his drought by finding the roof of the net with the final kick. "I am proud of my players and I feel sorry for the supporters because that was never a 5-1," said the Oldham manager.