But while the Irish province have come out on top on both occasions in Europe, it was a different story in the RaboDirect PRO12 as Scarlets won on the opening day 45-20 at Parc y Scarlets.
Leinster recovered from this opening defeat and head into the fourth clash with Simon Easterby's men sitting third in the RaboDirect PRO12 table.
And with Scarlets just three points and one place further back, centre O'Malley is urging his Leinster team-mates to carry their European dominance over the Welsh side over to the RaboDirect PRO12 league in order to stay on course for a semi-final spot.
"It was a good win at the weekend," said O'Malley, who made his first start of the season in the 40-5 victory over Treviso on Saturday.
"A lot of things went our way and Scarlets picked up a win themselves so will be a tough game this weekend.
"The Scarlets picked up a good win to beat Munster and obviously put in a good performance to do that.
"They beat us in the Rabo with a pretty similar group of players that they will have this weekend and that is in the back of our minds this weekend and we want to set that right really.
"The season is coming into a massively crucial stage. The top of the table is tight and this really is an eight pointer for us. They close in on us if they take the win and we don't want that."
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