|London Welsh (10) 13|
|Tries: Rowley Pens: Robinson 2 Cons: Robinson|
|Harlequins (12) 24|
|Tries: Dickson, Yarde, Sinckler, Williams Cons: Swiel 2|
Harlequins battled to a bonus point win at London Welsh to move up to eighth in the Premiership.
Scrum-half Paul Rowley gave Welsh the lead, but his opposite number Karl Dickson responded soon after for Quins.
England winger Marland Yarde crossed just before the break to give Quins the lead for the first time, before setting up prop Kyle Sinckler to dot down.
Two penalties from Will Robinson kept Welsh in the game, but Tom Williams came on to score Quins' fourth try.
The Exiles, who have been consistently shipping 50 points a match on their return to the Premiership this season, had the better of the opening exchanges and Yarde had to make a try-saving tackle on Nick Scott to stop Welsh taking the lead.
The hosts touched down soon after when Rowley latched onto Scott's offload, but Quins soon replied when Dickson's quick thinking from a tap-and-go penalty allowed him to cross over.
The visitors grabbed the lead just before half-time when they stole a line-out and centre Matt Hopper set up Yarde to cross for his third try of the season.
Quins began to get on top in the second half and Yarde's break set up prop Kyle Sinckler to touch down, and winger Williams scored on his return from injury to secure the bonus point.
London Welsh head coach Justin Burnell:
"We are not a team that going to roll over as you saw today.
"We've got nothing to lose now and hopefully our performances can improve to put us in good stead for next season.
"We showed great enthusiasm from the start and throughout. We were 10-5 up minutes before the half-time whistle but when you up against players of this calibre, things turn on a sixpence but we still weren't down in the dressing room at half-time."
Harlequins director of rugby Conor O'Shea:
"We played the youngsters so it's damned if you do or damned if you don't. We tried to play with ambition throughout the game and that's the way I want Quins to play even though it may not work at times.
"Welsh will beat someone this season and we didn't want to be that team.
"We got a bonus-point win so we are satisfied but we were inaccurate and very scratchy and probably played with too much width in the wrong areas of the field."
London Welsh: Robinson; Stegmann, Reynolds, Jewell, Scott; Weepu, Rowley; Trevett, Vella, Vea; West, Down; Browne, Kirwan (capt), Fonua.
Replacements: Britton, Reeves, Cooper, McCaffrey, Pienaar, Lewis, Barkley, Tincknell.
Harlequins: Lindsay-Hague; Yarde, Hopper, Lowe, Tikoirotuma; Swiel, Dickson; Lambert, Gray, Collier; Matthews, Twomey; Trayfoot, Clifford, Easter (capt).
Replacements: Buchanan, Marfo, Sinckler, Merrick, Chisholm, Care, Botica, Williams.
Referee: JP Doyle