Glasgow Warriors kept their nerve to secure a bye to a home Pro14 semi-final, while the Ospreys and the Scarlets are set to battle for the final European Champions Cup place.
The Pro14 regular season concluded on Saturday with Glasgow and Leinster topping the two conferences, securing an advantage heading into the knockout stage.
The Warriors got the result they needed against Edinburgh to top Conference A with second-placed Munster overcoming Connacht 27-14.
Tries from Sam Johnson, Ali Price, Niko Matawalu and Tommy Seymour secured a dominant 34-10 win against Edinburgh, who missed out on next season's Champions Cup.
In the quarter-finals Munster will face Benetton Treviso, who defeated Zebre 25-11 away, while Ulster will look to follow up a narrow win over Conference B leaders Leinster with victory against Connacht.
Debutant Marcus Rea scored his first senior try for Ulster to secure the bragging rights in a 14-13 triumph.
The big prize on offer elsewhere was qualification for the European play-off and the Scarlets joined the Ospreys despite a 34-32 defeat to the Dragons.
Two bonus points were all the Scarlets had to show for their efforts after a second-half collapse, Matthew Screech's 78th-minute try setting up Jason Tovey for the decisive conversion.
The Ospreys will have home-field advantage for the play-off after pipping Cardiff Blues with a 26-23 away win in similarly dramatic circumstances, as Sam Davies dispatched a last-gasp penalty.
The Cheetahs thrashed Southern Kings 61-25 in the day's other match.