Saracens (13) 45
Saracens flanker Kris Chesney is wrapped up by the Biarritz defence
Tries: Vyvyan, Jack 2, Penney, penalty
Cons: Jackson 3, Russell
Pens: Jackson 4
Biarritz (13) 16
Pens: Dupuy 3
Saracens are in touching distance of a first ever Heineken Cup quarter-final after a bonus-point win over Biarritz.
Romain Cabannes' converted try helped the visitors into a 13-6 lead but Sarries were level at the break thanks to Hugh Vyvyan's converted try.
Sarries blitzed Biarritz in the second half, Chris Jack and Rodd Penney both crossing before Jack's second score brought up the four-try bonus point.
Saracens added a fifth when Nigel Owens awarded them a last-minute penalty try.
Sarries will now travel to Glasgow for their final pool match with a five-point lead over the Warriors, who could only win 18-15 away to Viadana, at the top of the group.
Saracens began with width and adventure and they took the lead through a Jackson penalty after 15 minutes, only to fall behind from the re-start.
The hosts shipped the ball across the pitch in their own 22 in search of a better angle but Andy Farrell, fresh from signing a new two-year deal, dwelt too long on his clearance kick and was charged down.
Cabannes just managed to dot the ball down before it skittered out of the dead-ball area and Julian Dupuy converted and then added a penalty from near halfway when Sarries infringed after Richard Haughton tried to counter-attack.
Although Saracens were enjoying the majority of the possession they were struggling with the Biarritz defence and almost fell further behind when captain Neil de Kock's kick was charged down by fellow South African Trevor Hall.
The former Cats second row came within inches of scoring but the ball just eluded his dive and went dead.
Sarries went back on the attack and were rewarded when Biarritz infringed at a ruck and Jackson slotted his second penalty.
But, fearing yet another charge down, the hosts were penalised for blocking at a ruck from the re-start and Dupuy's second penalty made it 13-6.
It looked as though Saracens would trail at the break but with seconds remaining in the half they launched a sweeping attack.
Haughton, Farrell and Census Johnson all featured heavily and when they got quick ball from a ruck a Jackson dummy and half-break enabled him to feed Vyvyan and the second row powered over with a Biarritz defender hanging off him.
Jackson converted to make it 13-13 at half-time and in the second 40 minutes it was all Saracens.
They came desperately close to scoring when Haughton just failed to touch the ball down to finish off a long-range attack.
Biarritz managed to resist another sustained attack shortly but when they infringed after 48 minutes Jackson put Saracens back in front for the first time in nearly an hour.
The hosts pulled out a 10-point lead when All Blacks second row Jack saw the Biarritz defence part like the Red Sea after a surging attack led by Haughton and Ben Skirving.
Jackson converted and although Dupuy cut the gap with a penalty it was a rare bright spot for Biarritz.
Penney sliced through to score from distance on the hour mark, with Jackson converting to make it 30-16, and the fly-half added a penalty nine minutes later.
By now it was all Saracens and they claimed a bonus point when Jack plunged over from a ruck, and the last-gasp penalty try added an extra gloss to a superb second-half display.
Saracens boss Alan Gaffney:
"Some critics have pounded us for underachieving. It's a monotonous cry by certain people but we showed today that some of the criticism is unfounded.
"We haven't performed well over the last two weeks but we have the potential and I don't think we're underachieving.
"We like to play attacking rugby. Sometimes we put ourselves under pressure but that's how we want to play.
"Biarritz are no slouches. Look at the quality they have. I know they haven't been scoring many tries but they've tried to be more attacking recently.
"They pride themselves on their defence so I'm absolutely delighted that we managed to score five tries."
Saracens: Russell, Haughton, Sorrell, Barrell, Penney, Jackson, de Kock, Lloyd, Ongaro, Johnson, Jack, Vyvyan, Chesney, Hill, Skirving.
Replacements:: Kyriacou, Mercey, Ryder, Gustard, Dickens, Powell, Ratuvou.
Biarritz: Brusque, Bidabe, Cabannes, Traille, Ngwenya, Peyrelongue, Dupuy, Balan, August, Avril, Thion, Hall, Vahafolau, Harinordoquy, Cronje.
Replacements: Noirot, Lecouls, Malonga, Betsen, Cibray, Masi, Thiery.
Referee: Nigel Owens (WRFU)