Ronan O'Gara kicked all the points as Munster overpowered Harlequins 18-12 to book a Heineken Cup semi-final against Clermont Auvergne.
The two-time European champions produced a devastating second-half performance, led by captain Paul O'Connell and their dominant back row, to kill off any hopes Harlequins had of a famous victory.
Harlequins led 9-6 at the interval, courtesy of three Nick Evans penalties and although he slotted over another one in the second half, they were hit by a ferocious Munster onslaught. O'Gara, back at the venue of his first Heineken Cup match 14 years ago, kicked four penalties in a devastating 16-minute spell that Munster spent camped in Harlequins territory.
Harlequins boss Conor O'Shea had described this as the "biggest occasion" in the club's history The Stoop was packed to the rafters. The Harlequins scrum was dominant led by the Samoan tighthead James Johnston who earned an early penalty, which Evans converted. He pushed his next try, a 45-metre strike wide, but soon extended Harlequins' lead.
Munster's driving game had been effective but a spilled ball allowed Harlequins to counter-attack through Evans and then Nick Easter before Donnacha Ryan was penalised for not rolling away.
Munster moved the ball wide right to Casey Laulala who got outside Tom Williams. The ball went loose from his offload, Harlequins were penalised in the scramble and O'Gara slotted his first kick. Harlequins responded immediately. O'Connell spilled the kick-off, Johnston again proved too strong for Dave Kilcoyne in the scrum and Evans kicked his third penalty.
Easter and then Danny Care looked to trouble the Munster defence but the Harlequins scrum-half was caught holding on and it was the Irish province who finished the half with their tails up. O'Connell had defenders virtually hanging off him as he marched towards the Harlequins 22, eventually earning the penalty which O'Gara kicked.
If the score was tight at half-time, it was Munster who increasingly had the most influential players and that told in the 16 decisive minutes after the interval. O'Gara kicked four penalties in that time as Munster, playing with much greater urgency, dominated possession and took a match-winning grip on the game.
O'Gara kicked Munster into a 12-9 lead and Harlequins began to lose their composure, with poor passes from Evans and Williams landing Maurie Fa'asavalu in trouble. O'Gara extended the lead with his fifth penalty as Munster began to get dangerous runners Laulala and Simon Zebo into the game for the first time.
Harlequins full-back Mike Brown was floored by a shuddering tackle from James Downey as Munster kept their foot on Harlequin throats, with O'Gara opening a nine-point lead. Harlequins tried to gain a foothold and Evans replied with a penalty after a searing break from Williams and Tom Guest but Munster's defence simply suffocated them.