Harlequins (27) 42
Tries: Turner-Hall, Williams 2, Care, penalty, Brown Cons: Malone 3 Pens: Malone 2
Ulster (7) 21
Tries: Nagusa, Wallace, Trimble Cons: O'Connor 3
Care did his England hopes a power of good with a fine display for Quins
Harlequins moved to the top of Pool Four with a comfortable bonus-point Heineken Cup win at the Stoop.
Ulster made an electric start to the game, scoring after just 176 seconds through Fijian wing Timoci Nagusa.
But the home side responded strongly, Jordan Turner-Hall, Tom Williams, Danny Care and a penalty try putting Quins 27-7 ahead at half-time.
Mike Brown added another after the break and although Ulster mounted a revival, Williams completed the rout.
The victory puts Quins on nine points together with French side Stade Francais, who had earlier defeated the Scarlets in Paris.
And it sets up perfectly the clash between Stade and Quins at the Stade de France in the next pool game on 6 December.
The match was also notable for the display of scrum-half Care, who re-enforced his claim for the England number nine jersey in the autumn Tests with another sparkling display - scoring a superb opportunist try as well as setting up two others.
Ulster arrived at the Stoop only 45 minutes before the start because of heavy traffic but they took an early lead when Nagusa finished off after the ball was spread wide from a line-out.
Chris Malone replied for Quins with a penalty before Care's quick tap and break set up Turner-Hall for his second try of the season.
Ulster flanker Mike McCullough saw yellow after the visitors conceded yet another penalty and Quins took full advantage when Care sent Williams over in the corner.
Quins went further ahead went from another penalty touch, Care taking the line-out flick to burst through under the posts.
The bonus point was sealed just before the break when referee Tim Hayes awarded a penalty try for an obstruction by Darren Cave on Ugo Monye and Brown continued the scoring after half-time after winning the chase to a Williams kick.
Ulster never gave up though and crossed twice in the space of five minutes to reduce the deficit to 13 points.
Wing Andrew Trimble set up Wallace before scoring himself on 57 minutes after Cave's break.
But Williams dashed any hopes of a comeback when he collected Malone's crossfield kick for his second try.
Quins rugby director Dean Richards:
"I don't think the refereeing was unfair. I think the referee refereed it as he saw it.
"There was an exchange of comments between their captain and the referee at half-time and in the second half he came out and refereed it slightly differently at the breakdown which changed the game slightly. It became a lot messier after that.
"A couple of things we noticed about Ulster before we came into the game was that at times they could be ill-disciplined, that if they turned up here without a disciplined head on they would shoot themselves in the foot."
Ulster coach Matt Williams:
"At half-time the count was eight penalties, two free-kicks and a penalty try against us. "It's an 8-0 penalty count at half-time. Are you telling me that they did not infringe at the breakdown once in the first half?
"Quins scored two great short-kicking tries in the second half. All credit to them, great skill, but the referee influenced every other Quins score in that first half. The sin-binning was Matt McCullough's frustration coming out.
"We were competing for the ball and not getting the penalties, our scrum-half was getting hit by guys coming across the side and Quins really target the breakdown, very, very smart. But no team can cope with that ocean of possession against you.
"Officiating is just so difficult at this moment but you have to be very careful what you say as a coach. It is just totally inconsistent.
"We will put in a report. I don't talk to referees. It's like complaining to your mother-in-law about your wife. It doesn't get you too far."
Harlequins: Brown; T Williams, Monye, Turner-Hall, Amesbury; Malone, Care; Jones, Botha, Ross, Kohn, J Evans, Robshaw, Skinner, Easter.
Replacements: Masson for Monye (59), Luveniyali for Malone (72), Gomarsall for Care (63), Fuga for Botha (63), Lambert for Ross (66), Robson for Kohn (63), Guest for Robshaw (66).
Sin Bin: Care (51).
Ulster: Cunningham; Nagusa, Cave, Wallace, Trimble; O'Connor, Willis; Court, Best, Botha, Del Fava, Caldwell, McCullough, Pollock, Diack.
Replacements: Dewey for Wallace (66), Humphreys for O'Connor (63), Boss for Willis (66), J Fitzpatrick for Court (47), Brady for Best (72), O'Donoghue for Del Fava (47), Dawson for Pollock (53).
Sin Bin: McCullough (28).
Ref: Tim Hayes (WRFU).