Toulouse (16) 33
Tries: Fritz, Bouilhou, Heymans, Medard Cons: Elissade 2 Pens: Elissalde 3
Harlequins (7) 21
Tries: Brown, Monye 2 Cons: Evans 3
Cedric Heymans was a constant threat for the three-time winners
Harlequins suffered a heavy defeat as Toulouse booked their place in the quarter-finals of the Heineken Cup with a merciless attacking display.
The visitors started well and were ahead after 20 minutes through Mike Brown's break up the short side.
But Toulouse earned the bonus point they needed with Florian Fritz and Cedric Heymans particularly impressive.
Two fine tries from Ugo Monye polished the scoreline for Quins but a fifth consecutive defeat was already assured.
The hosts came into the game on the back of a home defeat of their own, 16-15 to French table-toppers Clermont Auvergne, and looked to make immediate amends.
A mammoth penalty attempt from Fritz and Jean-Baptiste Elissade's drop-goal both strayed wide in the opening five minutes as the scoreboard stayed blank.
John Andress's pressure at tight-head prop earned Nick Evans a shot at goal, but the New Zealander was similarly off target for the visitors who more than held their own in the opening exchanges.
Elissade missed another penalty on 15 minutes, but his next attempt sailed over to put Toulouse in front.
However, Quins, who are rooted to the bottom of Pool Five, surprised the home crowd as Evans sparked a break up the blind side.
The number 10 sent Tom Guest cantering away before James Percival drew the final defender to send Brown strolling under the posts.
Referee Nigel Owens waved away understandable protests from Toulouse over the final pass and Evans obliged with the extras.
Toulouse's dangerous backline provided an ominous response as a midfield scissors between Byron Kelleher and Heymans sliced open the Harlequins defence.
Some scrambling cover was required to prevent Yannick Jauzion crossing, but only at the cost of another Elissade penalty.
Ugo Monye showed his finishing skills to cross twice late on
Elissade slotted another to send his side in front, before Heymans snatched an interception from Nils Mordt's looping pass and fed Fritz, who scampered in to stretch the lead to nine points.
The Quins front row came under immediate pressure after the break and John Kingston introduced Chris Brooker and James Johnston in an attempt to reinforce the scrum.
But a break from Elissalde pinned them back on their own line once more and Thierry Dusautoir's beautifully weighted offload allowed his fellow flanker Jean Bouilhou to convert the pressure into a second try.
Kingston's tactical switch was undermined as prop Ceri Jones saw yellow for a professional foul on Elissade and the Toulouse pack easily stole a strike against the head to send Heymans over.
At a man down the Harlequins defence was in a constant state of emergency with the Toulouse runners revelling in the space.
The introduction of Frederic Michalak added a new dimension to the attack and he was heavily involved as Fritz poked a kick through for Maxime Medard to score the fourth try that secured their passage to the knockout stages.
Monye boosted his own reputation ahead of the Six Nations as he outpaced Yann David and chipped over Medard to score.
The winger's weaving run in the game's final piece of action shut the gap still further and earned the Londoners a flattering scoreline in a game that was never more than a dead rubber for them.
Harlequins head coach John Kingston:
"If they don't go all the way with the capacity they have to play at a top level, then they need to ask themselves some questions.
"I didn't think there was much between the sides in the first half and in fact, I thought we were on top in the contact area.
"Technically, our kicking game kept asking questions of how good a counter-attacking team Toulouse are.
"We had looked at how we would kick to them all week but in the end, we allowed them to get into broken field and some of their off-loading was fantastic.
"We could have lost by far more points than we did."
Toulouse: Medard, Donguy, Fritz, Jauzion, Heymans, Elissalde, Kelleher, Poux, Lacombe, Lecouls, Millo-Chluski, Albacete, Bouilhou, Dustautoir, Sowerby.
Replacements: Poitrenaud for Donguy (27), Michalak for Elissalde (56), Montes for Poux (64), Servat for Lacombe (50), Human for Lecouls (50), Lamboley for Millo-Chluski (41), Picamoles for Sowerby (67), David for Poitrenaud (68)
Harlequins: Brown, Strettle, Tiesi, Mordt, Monye, N. Evans, Care, Jones, Fuga, Andress, Percival, Robson, Guest, Skinner, Easter, Williams.
Replacements: Williams for Strettle (41), Dickson for Care (61), Brooker for Fuga (46), Johnston for Andress (46), Robshaw for Guest (52), Clegg for Williams (71).
Not Used: Croall, Stevenson.
Sin Bin: Jones (55).
Referee: Nigel Owens (WRFU)