Gloucester fought back from a 12-point half-time deficit to defeat Quins at Kingsholm.
The visitors scored four first-half tries, but three missed conversions from Chris Malone and two yellow cards cost them dearly as the Guinness Premiership leaders mounted a rousing fightback led by their pack.
The home side, featuring eight changes from their thrilling Heineken Cup defeat of the Ospreys, started poorly and Harlequins wasted no time in taking advantage. A couple of ruck infringements gifted Malone his first penalty two minutes into the game and five minutes later David Strettle’s pace did the damage.
Playing at outside centre for the second successive week, the England wing scythed through flailing tackles in midfield and combined with De Wet Barry to send Simon Keogh muscling over in the corner.
The next time he had the ball, Strettle wrong-footed Mike Tindall on the 22metre line and slipped past the waiting Olly Morgan before Andy Hazell got back to make the tackle.
But Quins were far enough advanced for the pack to secure quality ball and Malone’s grubber found Ugo Monye in space to dart over by the other flag.
Gloucester soon struck back when Chris Paterson’s deft inside pass to Anthony Allen had the young centre sucking in the defence before he fired the ball out for Lesley Vainikolo to run in his first try at Kingsholm.
Paterson, having earlier missed a penalty, sent over the conversion, but Quins were finding plenty of holes to exploit. With Andy Hazell sin-binned for a high tackle on Monye, the visitors added another 12 points with Gloucester only able to add a Paterson penalty .
Malone took Andy Gomarsall’s pass from the scrum and ran straight through Gareth Cooper and Paterson to score, adding his only conversion of the half. Then Keogh sprinted down the narrow side after a five-metre line-out to nail the bonus-point try in the 33rd minute.
Paterson’s second penalty followed Hazell’s return and Gloucester finished the first half with a couple of searing breaks and a powerful drive by Vainikolo, but were unable to close Quins’ 25-13 lead at the interval.
Maintaining their momentum, Gloucester sent Tindall over six minutes into the second half, with Paterson converting, as their pack took control of the game.
Quins conceded a raft of penalties and lost Gomarsall and Ceri Jones to the sinbin as the pressure came to bear from a series of scrums and penalty line-outs within 10 metres of their posts.
Eventually it proved too much as Vainikolo picked up from a ruck and stepped around Chris Robshaw to score his second try. Paterson’s conversion put Gloucester two points ahead with 20 minutes remaining and with Malone skewing a 25m drop-goal, it left the league leaders to run down the clock.