Noel Reid and Jordi Murphy also crossed the whitewash as Leinster completed a 27-0 win on Friday night to ensure they could not be overtaken by rivals Munster.
Munster kept pace with the leaders but lost some ground as they could only manage a 14-3 win at home to struggling Benetton Treviso.
Keith Earls scored an eye-catching try on his return to RaboDirect PRO12 action and James Downey also dotted down but they rarely looked like reaching the four-score mark.
In an all-Welsh clash on Friday it was all Ospreys as Aisea Natoga grabbed a hat-trick of tries to sink Cardiff Blues at the Liberty Stadium.
The 34-9 win, in which Wales internationals Rhys Webb and Ashley Beck also scored, keeps Ospreys in the top four and well in the hunt for a playoff spot.
Connacht's resurgence continued with an impressive 24-8 victory at Rodney Parade, as their forwards dominated Newport Gwent Dragons.
Captain John Muldoon scored twice as Connacht, who were rock bottom not too long ago, recorded their fourth straight RaboDirect PRO12 win to move up to seventh in the table.
There were also wins for title hopefuls Ulster and Glasgow Warriors, who saw off Edinburgh and Scarlets respectively in a pair of low-scoring contests.
TRY OF THE WEEKEND
There were three to choose from but on of Ospreys winger Natoga's tries against Cardiff Blues stood out from the crowd.
With the score at 7-0 Natoga opened his account for the evening with a neat piece of footwork following great vision from Webb.
With the Ospreys pack piling towards the line, Webb's quick thinking saw the scrum-half send a grubber through a gap in the Blues defence.
Natoga still had work to do but with a perfectly-weighted through ball of his own he was able to avoid the attentions of the defender and dot down.
BREAK OF THE WEEKEND
Keith Earls made a scoring return to RaboDirect PRO12 action and, despite suspicions of a forward pass, his try was easy on the eye.
JJ Hanrahan, who was having an off-day from the tee, made a cutting break through the Treviso line and sped towards the last man.
And with Earls waiting on his left shoulder, the fly-half had the simple task of offloading for the game's first try.
PLAY OF THE WEEKEND
Fitzgerald grabbed a pair of tries for Leinster but it was the man on the other wing who provided the most eye-catching piece of powerful running.
After Ian Madigan sent a high ball over to the right wing Darragh Fanning collected the ball and found his way past three separate defenders.
The winger was eventually brought down but, despite a lack of support, forced Tommaso Iannone to concede the penalty - the Zebre man even saw a yellow card for his troubles.
PLAYER OF THE WEEKEND
He may have been outdone by Natoga's hat-trick but Connacht's Muldoon bagged a pair of tries in a superb captain's performance.
Pat Lam's side march on up the table and their forward pack are largely to thank, regularly overpowering their Newport counterparts on Sunday.
Muldoon was the chief beneficiary, on hand to dot down twice, and it was no less than he deserved for leading from the front.
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