Glasgow Warriors stretched their lead at the top of Conference A to nine points thanks to Nikola Matawalu's hat-trick against Ospreys.
Zebre stunned Edinburgh, Scarlets denied Southern Kings and there was landmark win for Ulster in Pro14 on Friday.
Leinster are five points clear at the top of Conference B after the defending champions beat Munster at the Aviva Stadium.
Leinster's Pro14 title defence continued with a fourth win in five, with Glasgow Warriors and the Ospreys matching that return on Saturday.
Edinburgh saw off Connacht to record their first Pro 14 win as Munster thrashed a much-changed Ospreys side on Friday.
Bryan Byrne's late try and Ross Byrne's subsequent conversion saw champions Leinster snatch victory over Cardiff Blues in the Pro14.
Wales assistant coach Shaun Edwards will juggle his international commitments with a role at the Ospreys in the Pro14 this season.
The departing Dan Biggar became the leading Pro14 points scorer but he was unable to stop UIster sealing a Champions Cup place.
Wales international George North will swap Northampton Saints for Pro14 side the Ospreys, the WRU has announced.
Wales international George North will swap Northampton Saints for Pro14 side the Ospreys, the WRU has announced.
Nick Timoney's last-gasp try secured Ulster a crucial bonus-point victory over Glasgow Warriors on Saturday.
Johan Goosen's return to rugby was spoiled by Munster, who engineered an impressive second-half turnaround at the Cheetahs in Pro14.
Edinburgh were beaten at home by Ulster in the Pro14, while the Ospreys thumped Connacht in Swansea.
Leinster suffered a surprise Pro14 defeat against Ospreys on Saturday, while Cardiff Blues won for a fifth game in a row.
Set to join Toulon at the end of the season, injury looks to have ended Rhys Webb's time in Welsh rugby.
Ahead of Wales' final Six Nations match, Alun Wyn Jones has signed a new NDC, meaning he will continue to represent the Ospreys.