Two-time defending champions Leinster crashed out of the Heineken Cup after Munster beat Racing Metro, while Saracens and Leicester progressed.
Simon Zebo scored a hat-trick of tries as Munster swept past 14-man Racing Metro 29-6 to reach the quarter-finals stage and knock Leinster out of in the process.
Rob Penney's men needed a bonus-point win at Thomond Park in order to leapfrog their Irish rivals into the second best runners-up spot.
Racing were forced to play without Antoine Battut for 74 minutes in Limerick, the flanker earning an early red card for a knee to the head.
A trio of first-half tries, topped off by Mike Sherry's first Heineken Cup score, handed Munster a deserved 17-6 interval lead.
Gaetan Germain landed a brace of penalties for the visitors, but the home side took their try tally to five as man of the match Zebo grabbed his second European hat-trick.
Charlie Hodgson's late try gave Saracens a bonus-point 40-7 win as they sealed their progress to the last eight of the Heineken Cup with an easy victory over Edinburgh.
Sarries made light of the snowy conditions that threatened to blight their last-ever game at Vicarage Road, scoring five tries to qualify from the pool stage for the second season in a row.
Chris Ashton gave himself a timely boost two weeks before the start of the RBS 6 Nations with two of the tries, with Sarries' other scores coming from Matt Stevens and Chris Wyles.
Leicester Tigers clinched the final Heineken Cup quarter-final spot at the expense of Toulouse after edging the winner-takes-all Pool Two clash 9-5 at Welford Road.
In a match played out in atrocious conditions on Sunday afternoon, Toby Flood kicked three penalties for Leicester while Toulouse, who scored the game's only try through Yoann Huget, were left to rue a misfiring display in front of goal.
Toulouse will be wondering how they failed to progress after wasting five kicks at goal during the 80 minutes.
Andrea Pratichetti crossed late as Treviso fought back to snatch a shock victory 17-14 over the Ospreys.
The Welsh region appeared on course to finish their Heineken Cup campaign on a high thanks to Tom Isaacs' try and the boot of Dan Biggar.
But Treviso launched a late comeback with 14 unanswered points in the final five minutes of a previously uneventful clash at a muddy Stadio Comunale di Monigo.
First Alessandro Zanni crossed the whitewash following a sustained period of pressure and the Italians completed their miraculous recovery with Pratichetti's intervention with just five seconds to spare.
Heineken Cup quarter-final line-up: Harlequins v Munster, Clermont Auvergne v Montpellier, Toulon v Leicester, Saracens v Ulster.
Ties to be played April 5-7.
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