Gloucester confirmed powerful Heineken Cup quarter-final credentials by grounding Ospreys in a gripping battle at Kingsholm.

The Guinness Premiership leaders recovered from conceding two first-half tries - both scored by Ospreys centre Sonny Parker - to take a firm grip on Pool Two.

They have collected nine points from a possible 10 ahead of back-to-back appointments with enigmatic French outfit Bourgoin next month.

The Ospreys led 12-6 approaching half-time, but Gloucester delivered an immense second 40 minutes.

England internationals Anthony Allen and James Simpson-Daniel scored stunning tries, while fly-half Ryan Lamb kicked 11 points before replacement Chris Paterson landed a conversion and penalty.

Gloucester, at times oozing class, moved up through the gears when they needed to, and the Ospreys - despite their galaxy of international talent - could not respond.

It was a bruising, no-holds-barred encounter, which ultimately went Gloucester's way through their superior physicality and greater sense of adventure behind the scrum.

Gloucester welcomed back Italy's World Cup skipper Marco Bortolami - he replaced injured lock Alex Brown - but they fielded the same back division that tore Ulster apart in Belfast last Friday night, including a home debut for rugby league recruit Lesley Vainikolo.

The Ospreys were without Wales wing Shane Williams, who was absent due to a thigh injury that could threaten his participation in next weekend's Millennium Stadium clash against world champions South Africa.

Gloucester boss Dean Ryan had predicted a "firecracker" contest, and the early exchanges did not disappoint in front of a record Kingsholm crowd for rugby union's professional era - 16,500.

But Gloucester, who posted five tries inside the opening 25 minutes at Ulster's expense, were on the receiving end this time around.

Parker pounced from Ospreys' first significant attack, capitalising when centre Mike Tindall's wild pass flew too high for Iain Balshaw, and the former Wales midfield man weaved his way over.

James Hook converted, and although Lamb slotted his opening penalty, Ospreys came within inches of extending their lead when wing Jonny Vaughton dived for the corner, yet Balshaw just nudged him into touch.

A second Lamb penalty further narrowed the deficit, yet it proved a false dawn for Gloucester fans as quality approach work by Ospreys' former All Blacks flanker Marty Holah allowed Parker another chance, which he took magnificently.

Hook failed to land the extras, but Gloucester stayed in contention - despite conceding considerable territory and making more than twice the first-half tackles of their opponents.

Vaughton was sin-binned during injury time for failing to roll away after he brought down Gloucester's Fiji flanker Akapusi Qera, and Lamb narrowed the gap to 12-9 through another penalty.

The Ospreys could only kick themselves for not being further ahead, especially having delivered the game's three dominant figures in Parker, Holah and scrum-half Mike Phillips.

And Gloucester quickly deepened their sense of frustration by striking from deep.

Ospreys' midfield defence couldn't cope with Allen's guile, and a devastating sidestep took him clear on a 60-metre sprint to the line.

Lamb converted, before a Hook penalty made it 16-15, but only after Gloucester flanker Alasdair Strokosch fortuitously avoided punishment following a cynical trip on Ospreys full-back Lee Byrne.

Hook then hoisted the Ospreys ahead after Gloucester prop Carlos Nieto was yellow-carded for killing possession. It proved though, a short-lived advantage.

Hook turned villain just three minutes later, attempting an aimless kick deep inside Gloucester's half, and the resulting counter-attack left Ospreys defenders floundering.

Balshaw and Tindall had the confidence and vision to run from deep, with their adventure rewarded as Simpson-Daniel finished off in the corner.

Paterson, on as a substitute for Lamb, booted the conversion, opening up a five-point lead to leave the Ospreys under pressure in their quest for a priceless away win.

And Paterson's 73rd-minute penalty sealed the deal, ending a pulsating contest that saw Gloucester deservedly triumph.