Saracens outscored Harlequins five tries to two to win 39-17 and go top of the Premiership standings in front of a world-record crowd at Wembley on Saturday.
A clinical first-half display from Saracens saw them go in at half time 27-10 up, through tries from Chris Ashton, George Kruis and Owen Farrell, with Karl Dickson's try and Nick Evans's penalty keeping Quins within touching distance.
The second half was a more low-key affair, with Sam Smith's converted try putting Harlequins within 10, but Jacques Burger and Marcelo Bosch sealed the victory for Saracens.
The game had a staggered start as David Strettle was on the receiving end of a swinging arm from Maurie Fa'asavalu, leaving the winger unconscious for a lengthy period of time, forcing him to be carried off on a stretcher.
Soon after, Nick Easter tried to make the most of a poor pass, but could only palm it into the path of Ashton who, after fending off Ugo Monye, dived over to score a 70-metre try, with Farrell converting.
Harlequins were awarded a penalty inside from 20 metres out, with Evans successfully converting to close the gap. Sarries hit back with a penalty of their own as Farrell scored from over 40 metres out, re-establishing their seven-point lead, before scoring again shortly after as Kruis powered through Nick Kennedy to touch down under the posts.
After a good period of possession near the Saracens try line, Dickson squeezed through a gap in the Sarries defence to touch down and close the gap, with Evans converting.
Both sides could have counted themselves lucky to still have 15 men on the pitch when Joe Marler held down Richard Wigglesworth, who swung an arm in retaliation.
Farrell plucked Evans's careless pass out of the air to score under the posts, before converting his own try to go in 27-10 up at the break.
Quins immediately made use of the numerical advantage as Steve Borthwick was sent to the sin bin, and Smith went over in the corner just seconds later.
Saracens secured a bonus point as Berger powered over the line after good movement from Schalk Brits, before Bosch found space to go over under the posts with Farrell converting with the last kick of the game.
Tries: Ashton, Kruis, Farrell, Burger, Bosch
Cons: Farrell 3, Hodgson
Pens: Farrell 2
Yellow card: Borthwick
Tries: Dickson, Smith
Cons: Evans 2
Saracens: 15 Alex Goode, 14 Chris Ashton, 13 Marcelo Bosch, 12 Brad Barritt, 11 David Strettle, 10 Owen Farrell, 9 Richard Wigglesworth, 8 Ernst Joubert, 7 Jacques Burger, 6 Jackson Wray, 5 George Kruis, 4 Steve Borthwick (c), 3 James Johnston, 2 Schalk Brits, 1 Mako Vunipola.
Replacements: 16 Jamie George, 17 Richard Barrington, 18 Matt Stevens, 19 Mouritz Botha, 20 Kelly Brown, 21 Neil de Kock, 22 Charlie Hodgson, 23 Duncan Taylor.
Harlequins: 15 Ollie Lindsay-Hague, 14 (23) Sam Smith, 13 Matt Hopper, 12 Tom Casson, 11 Ugo Monye, 10 Nick Evans, 9 Karl Dickson, 8 Nick Easter (c), 7 Luke Wallace, 6 Maurie Fa'asavalu, 5 George Robson, 4 Nick Kennedy, 3 Kyle Sinckler, 2 Joe Gray, 1 Joe Marler.
Replacements: 16 Dave Ward, 17 Mark Lambert, 18 Paul Doran Jones, 19 Joe Trayfoot, 20 Tom Guest, 21 Sam Stuart, 22 Louis Grimoldby, 24 Jordan Turner-Hall.
<Venue: Wembley Stadium, London
Referee: JP Doyle
Assistant Referees: Roy Maybank, Andrew Pearce
TMO: Sean Davey