Ulster were the only victorious Irish side this weekend.
Benetton Treviso 11
Ruan Pienaar once again showed Ulster what they will be missing next season as he produced another top class display against Treviso.
The South African scrum-half scored a try, a penalty and two conversions to score 12 of his sides 22 point total.
Rob Herring and Luke Marshall had crossed the whitewash earlier to put Ulster in the driving seat before Pienaar dotted down for a third, however, they couldn't find that elusive fourth try that would have secured a precious away bonus point.
In truth, it was a comfortable away day for last year's Pro12 semi-finalists, as Treviso rarely threatened their line, with Marco Barbini grabbing a consolation try with the last play of the game.
The result leaves Ulster second, and Treviso bottom of the table.
Connacht's disappointing start to the season continued as they suffered a second home loss in succession tonight in Galway.
The Pro12 champions looked out of sorts once again and trailed at the break by 10-3, with Rhys Webb scoring the half's only try.
The second half saw an improvement from the Westerners, as Eoin McKeon finished an excellent team move to nudge the hosts in front, but it only lasted a matter of minutes as Sam Davies kicked his second penalty of the evening to put the Welsh region back in front.
Then the floodgates opened as Ospreys scored three tries in the final 10 minutes as Tyler Ardron, Jeff Hassler and Webb made sure of the bonus point before the clock went red.
Thje result leaves Connacht rooted to the bottom of the table with zero points registered and a score difference of -57.
Glasgow Warriors 33
Tommy Seymour scored four tries to continue his red hot form and help Glasgow to a thrilling victory over Leinster at Scotstoun Stadium.
The Scottish international opened the scoring in the left corner before Leinster went on to dictate first half proceedings, with Rob Kearney and Tim Swinson exchanging tries, before Josh Van Der Flier and Zane Kirchner touched down before the break.
After the interval, Glasgow were on top as Seymour seized on two Leinster errors to complete his hat-trick, before adding a fourth late in the game to seal victory.
Cardiff Blues 24
Munster suffered a surprise home defeat thanks to a late Dan Fish try at Irish Independent Park on Friday night.
Tries from Andrew Conway and Dave Kilcoyne, as well as 10 points from the boot of Ian Keatley had Munster leading entering the final quarter of the game, but the Blues were still in the game with two Tom James tries keeping them in touch.
In what was a fascinating battle, a slick backline move down the left touchline saw Fish break free to put the visitors in command, and despite another Keatley penalty, they managed to hold out.