A try double from Ashley Beck plus a further score from prop Paul James helped the hosts to a 27-3 lead shortly after the interval.
Treviso, for whom Kris Burton kicked a first-half penalty, replied with a Ludovico Nitoglia try but the Ospreys completed the scoring with Joe Bearman and replacement Tom Isaacs adding further tries as fly-half Dan Biggar finished with 16 points.
The hosts, buoyed by a superb win in Leinster last week and the return to the side of wing Shane Williams for his first game since January, started with plenty of tempo in their play.
Biggar and Burton exchanged early penalties before the Ospreys grabbed the first try.
The fly-half launched an up-and-under and did brilliantly to reclaim the ball in the air before swivelling to find Hanno Dirksen, who in turn passed inside for Beck to canter over for a converted score.
Another Biggar penalty rapidly followed and the Ospreys registered their second try before the half-hour mark through prop James.
It was his front-row colleague Adam Jones who set up the score, as the tighthead wriggled through a tackle on the edge of the Treviso 22 before passing to James when he perhaps could have scored himself.
James rumbled his way over for the score to be awarded by video referee Tony Rowlands, despite appearing to lose the ball as he was rolled over in Alberto Sgarbi's last-ditch tackle, for a 20-3 interval lead
The Ospreys were again over the line just two minutes into the second half. Williams' chip ahead turned the Treviso defence, and when the ball was turned over the winger moved it wide for Andrew Bishop to put Beck in for his second try of the night, again converted by Biggar.
Having spent almost the entire evening on the back foot Treviso then produced the try of the game as scrum-half Edoardo Gori capitalised on turnover ball to launch a thrilling attack from their own 22.
The Italy international weaved in and out of tackles to take play to the other end of the field where a wide pass from replacement Luke McLean saw Nitoglia cut inside some weak tackling for a try converted by fly-half Alberto Di Bernardo.
The Ospreys were being frustrated in their efforts to find a bonus-point clinching fourth try, and those frustrations increased when Treviso wing Tommaso Benvenuti's cynical knock on prevented a score in the corner.
The Italy cap saw yellow for his trouble and the Ospreys decision to take a scrum paid off as they marched Treviso over their own line for Bearman to dot down for another converted score, giving the Ospreys their first winning bonus point in the league this season.
The fifth try came seconds later as Williams, Beck and replacement Isaacs linked beautifully down the left flank for the latter to cross in the corner, with Biggar keeping his 100% record with the boot intact by landing the touchline extras.
In the night's other match
Jonathan Sexton and Fergus McFadden kicked closing penalties and Ian Madigan, another of Leinster's talented reserves, landed a fine drop goal to seal only the province's second win at Thomond Park since 1995.
A series of unsettled scrums and unforced errors made for a scrappy first 40 minutes dominated by referee Nigel Owens' whistle and Sexton's right boot, with Leinster establishing a 9-3 interval lead.
Owens sin-binned props Marcus Horan and Mike Ross early in the second period and Munster reacted best with O'Gara getting the home side back on terms.
However, with Joe Schmidt unloading an experienced bench, Leinster exerted enough control in the closing stages with man-of-the-match Isa Nacewa the leading attacking threat.
This top of the table clash got off to a typically breathless start with two turnovers in the opening minute and an early try-scoring opportunity for Rob Kearney, who knocked the ball over the try-line as he tried to gather Sexton's well-weighted kick.
The visitors enjoyed the best of the early territory and Sexton kicked them ahead with a long-range penalty in the 10th minute.
It took over 20 minutes for the scrum to settle with Ireland internationals Horan and Ross going down together on a number of occasions. A decision against the latter went unpunished when O'Gara hit the left-hand upright.
A bout of loose kicking did little for the game as a spectacle, and while there was a distinct lack of continuity the contest at the breakdown was as ferocious as ever.
Munster got on the front foot after the welcome sight of a clean scrum. Sean Cronin infringed at a ruck in the Leinster 22 and O'Gara duly punished him with the levelling penalty from the right.
Munster were guilty of going off their feet at ruck time on the restart, allowing Sexton to swiftly restore Leinster's three-point advantage.
Leinster began to put more phases together in attack as half-time approached, with Gordon D'Arcy, on his 200th appearance, and Kevin McLaughlin carrying well.
A third penalty success for Sexton, after Horan dropped a scrum, put six points between the sides at the break.
Both Horan and Ross saw yellow three minutes into the second half as referee Owens lost his patience with the pair.
The next scrum saw Heinke van der Merwe infringe and O'Gara made no mistake with his kick from 40 metres out.
Munster gained some much-needed momentum in the third quarter with replacement Wian du Preez steadying the scrum.
O'Gara missed his next shot at the posts, but was back on target in the 54th minute to level the game after Brad Thorn was penalised for a high tackle.
By the hour mark, Leinster had issued a strong response with Nacewa and Sexton threatening from purposeful attacks. The latter then kicked his final penalty to make it 12-9 before being replaced by Madigan.
Leinster's lead may have been a narrow one but there was a better flow to their game at this stage, and Nacewa was soon sprung through a gap from a lineout forcing Munster to scramble back.
A BJ Botha scrum infringement led to McFadden, Sexton's place-kicking replacement, landing a 70th-minute penalty for 15-9 and the tide was turning blue.
Leinster's experienced bench was a key factor as they ground out the result. A short burst from Cian Healy led to fellow replacement Madigan sending over a snap drop goal and the fast-breaking McFadden was a pass away from creating a late try.