London Irish never recovered from going down to a 0-17 deficit in the first 15 minutes, losing 7-22 in the Guinness Premiership on Friday, with the bonus-point win taking Sarries third in the table.
Left wing Kameli Ratuvou, Full back Thomas Castaignede and fly-half Glen Jackson, who also landed a conversion, were the scorers as free-flowing Saracens shredded the Irish defence.
But the visitors had to wait until the 76th minute before Dan Scarbrough kicked through for replacement winger Tomas de Vedia to score their fourth try in the corner and secure what could yet prove to be a vital bonus point in their bid for a place in the Championship top-four play-offs.
The final strike by Saracens ended any lingering hope for Irish, whose second-half revival was sparked by a try and conversion from full-back Delon Armitage.
Ratuvou, the Fijian flyer, struck the first blow in the third minute with his third Premiership try of the week.
Scarbrough set up the chance and Ratuvou, scorer of two tries in Sunday's 36-5 home victory over Bristol, left Armitage standing as he raced past him.
Scarbrough was the provider again in the 11th minute when he kicked ahead after Irish spilled the ball in the Saracens half and won the 60-metre chase to send France international Castaignede in for the second try.
Four minutes later Jackson touched down following a spell of Saracens pressure which began when Irish's England fly-half discovery Shane Geraghty hesitated momentarily and was beaten to a bouncing ball on the halfway line by former Ireland hooker Shane Byrne.
The 20-year-old Geraghty endured a torrid return from Six Nations duty.
He saw an eighth-minute penalty kick rattle the post and rebound into play, failed with a first-half drop goal attempt and then knocked on after right-wing Topsy Ojo penetrated the Saracens midfield.
Geraghty's misery finally came to an end when he limped off in the 43rd minute to be replaced by Nils Mordt, after Ojo has squandered a three-man overlap by knocking on.
Irish finally pulled themselves back into the game when replacement flanker Declan Danahar drew two Saracens players to release Armitage on a 30-metre run for his try.
Armitage narrowly missed a penalty from the halfway line but the home side's hopes were nullified by in-form Saracens who have now only lost one of their last seven Premiership matches.
They were denied a fourth when Ratuvou put a foot in touch as he burst down the left wing, but the bonus point was eventually obtained courtesy of de Vedia.
For London Irish:
Tries: Ratuvou, Castaignède, Jackson, De Vedia
London Irish: 15 Delon Armitage, 14 Topsy Ojo, 13 Seilala Mapusaua, 12 Riki Flutey, 11 Sailosi Tagicakibau, 10 Shane Geraghty, 9 Paul Hodgson, 8 Juan Leguizamon, 7 Olivier Magne, 6 Kieran Roche, 5 Bob Casey (c), 4 James Hudson, 3 Tonga Lea'aetoa, 2 Robbie Russell, 1 Neal Hatley.
Replacements: 16 Michael Collins, 17 David Paice, 18 Nick Kennedy, 19 Phil Murphy, 20 Declan Danaher, 21 Barry Everitt, 22 Nils Mordt.
Saracens: 15 Thomas Castaignede,14 Dan Scarbrough, 13 Kevin Sorrell, 12 Adam Powell, 11 Kameli Ratuvou, 10 Glen Jackson, 9 Neil de Kock, 8 Ben Skirving, 7 Richard Hill, 6 Kris Chesney, 5 Simon Raiwalui (c), 4 Iain Fullarton, 3 Cencus Johnston, 2 Shane Byrne, 1 Kevin Yates
Replacements: 16 Matt Cairns, 17 Tom Mercey, 18 Hugh Vyvyan, 19 David Seymour, 20 Moses Rauluni, 21 Rodd Penney, 22 Tomas de Vedia
Referee: Chris White
Touch judges: Paul Emerson, David Kurk
Television match official: Bob Ockenden