Catalans Dragons (8) 38
Tries: Elima, Pelo 2, Bosc, Baile, Bell, McGuire Goals: Bosc 5
Harlequins (0) 16
Tries: Esders, Gale, Haggerty Goals: Gale 2
Harlequins slumped to their fifth consecutive defeat as Catalans Dragons accelerated to a comfortable victory, thanks to five second-half tries.
Quins defended well but were edged out despite tries from Ryan Esders, Luke Gale and Gareth Haggerty.
Dimitri Pelo crossed twice for the French side while Olivier Elima, Thomas Bosc, Jean-Philippe Baile, Steven Bell and Casey McGuire also touched down.
Catalans' fifth win in seven lifts them to 10th, while Quins are now eighth.
Catalans dominated the opening half but led only 8-0 at the break after a determined rearguard action from the Londoners in fierce heat.
The French broke through in the 14th minute when Elima held off Will Sharp to touch down after being put through by Bosc.
Yet it was not until the stroke of half-time that the hosts were able to double their advantage as the outstanding Greg Bird offloaded to put Pelo over in the corner.
The Dragons appeared to take a decisive lead early in the second half as Baile shrugged off two tackles to find Bosc, who in turn set up Pelo's second.
Jamie O'Callaghan had a try disallowed for a forward pass as Harlequins responded but the visitors did get on the scoreboard as Esders, on loan from Hull KR, pounced from a Matt Gafa kick.
The recovery was brief as Bosc extended the Dragons' advantage with a superb individual effort, twice kicking forward and regathering to go under the posts.
Gale intercepted to race half the length of the field for Harlequins' second but the game drifted beyond them as Baile powered in from an Elima pass.
Bell stretched the advantage further by scoring in the corner after Clint Greenshields cleverly spread the play wide.
Haggerty barged over from close range for a Harlequins consolation but the hosts had the final word as McGuire found his way to the line.
Bosc capped a fine individual performance by kicking his fifth goal.
Catalans Dragons: Greenshields, Stacul, Bell, Baile, Pelo, Bird, Bosc, Ferriol, McGuire, Ryles, Elima, Gossard, Carlaw. Replacements: Perry, Mounis, Fakir, Casty
Harlequins: Melling, O'Callaghan, Clubb, Wells, Sharp, Gafa, Gale, Temata, Kaye, Ward, Robinson, Esders, Golden. Replacements: McCarthy-Scarsbrook, Haggerty, May, Skee.
Referee: S Ganson (St Helens).