Saracens' South African duo of Neil de Kock and Brent Russell proved too much for Harlequins to handle on Saturday, with Sarries taking the Guinness Premiership London derby 27-20 at the Stoop.
Quins, without a win in their previous seven matches - six of them in the Heineken and EDF Energy Cup competitions - since beating European champions Wasps 26-25 on October 20 were desperate to recapture the form which had taken them to fifth place in the Premiership table.
Expertly orchestrated by England scrum-half Andy Gomarsall, they dominated the opening half hour but - not for the first time this season - failed to turn early pressure into points.
All they had to show for their first half efforts was a penalty from Jarvis after a desperate Saracens defence strayed offside in front of their own posts.
But the visitors well-drilled rearguard soaked up the pressure, stopping England winger David Strettle and South African hooker Gary Botha just short of the try-line.
Jackson equalised 16 minutes later on the half hour when Quins' Welsh prop Ceri Jones was penalised for bringing down a scrum
Then, against the run of play, Saracens scored the opening try.
Their hard-working Samoan front-row forward Cencus Johnston demonstrated the skill allied to his power as he created space on the half-way line to relieve Kameli Ratuvou.
The Fijian World Cup winger kicked ahead as the Harlequins cover closed him down and referee Tony Spreadbury controversially awarded de Kock the touchdown despite prolonged protests from the home supporters who claimed Monye got his hand on the ball first.
Jackson converted and it would have been even worse for Harlequins had the fly-half not missed two penalty kicks, including a simple effort which rebounded from the post.
Skipper de Kock then showed his defensive qualities match his try-poaching ability with a last-ditch tackle on fellow South African De Wet Barry, bringing the Quins centre down just short of the line.
Jarvis and Jackson exchanged penalties at the start of the second half before the fast-moving Saracens backs combined to deliver what proved to be the crucial blow in the 52nd minute.
Centre Kevin Sorrell, taking a pass from Jackson, embarked on a looping run to split the Quins defence and sent full-back Russell, making up for lost time after missing the first three months of season with a broken collarbone, racing in for a try.
At the other end of the pitch Russell turned try-saver with a desperate tackle, two metres from the line, on Harlequins flanker Will Skinner who had run to the half-way line after grabbing an interception.
But Harlequins were not to be denied and the resulting pressure paid off with a 59th minute try for Fuga, who had only been on the pitch for two minutes, as he ignored the four unmarked backs outside him to neatly spiral inside and force his way over the line.
But any hopes of a home fight-back were dashed as Penney, another effective replacement, scored Saracens third try after Jackson created the opening.
Harlequins never gave up with Monye grabbing a late converted try but it was too little too late.
Tries: Fuga, Keogh
Cons: Jarvis 2
Pens: Jarvis 2
Tries: De Kock, Russell, Penney
Cons: Jackson 3
Pens: Jackson 2
Harlequins: 15 Mike Brown, 14 David Strettle, 13 De Wet Barry, 12 Jordan Turner-Hall, 11 Ugo Monye, 10 Adrian Jarvis, 9 Andy Gomarsall, 8 Nick Easter (capt), 7 Will Skinner, 6 Chris Robshaw, 5 Jim Evans, 4 Ollie Kohn, 3 Mike Ross, 2 Gary Botha, 1 Ceri Jones.
Replacements: 16 Tani Fuga, 17 Ricky Nebbett, 18 James Percival, 19 Chris Hala'ufia, 20 Paul Volley, 21 Steve So'oialo, 22 Simon Keogh.
Saracens: 15 Brent Russell, 14 Richard Haughton, 13 Kevin Sorrell, 12 Andy Farrell, 11 Kameli Ratuvou, 10 Glen Jackson, 9 Neil de Kock (capt), 8 Ben Skirving, 7 Richard Hill, 6 Kris Chesney, 5 Chris Jack, 4 Hugh Vyvyan, 3 Cencus Johnston, 2 Fabio Ongaro, 1 Nick Lloyd.
Replacements: 16 Andy Kyriacou, 17 Cobus Visagie, 18 Tom Ryder, 19 , 20 Moses Rauluni, 21 Adam Powell, 22 Rodd Penney.
Referee: Tony Spreadbury