The slender one-point victory moved the 2006 and 2008 champions four points clear of Perpignan at the top of Pool 1, leaving the French side desperate to win next weekend's return fixture on home soil.
To stand any chance they will have to cut down on their indiscretions - O'Gara had nine kicks at goal and spurned three others - and build on their 3-0 try count.
"We made hard work of it and we conceded 20 points not really through their creative play, but from our errors," said O'Gara afterwards.
"We have a fair bit of work to do. We thrive on cup rugby and our consistency over the past 10 or so years has meant the target is the knock-out phase at least in this competition.
His seven penalties equalled his Munster European record, set in the quarter-final win over another French side, Biarittz Olympique, in 2001.
So, maybe those people who thought he was past his best when he missed those kicks against the Ospreys in the Magners League last weekend had better think again.
"Kicking is a fascinating subject for me. I guess over the past five years I have been up around the 80% success rate, which means the next challenge is to reach 90%," added Ireland's record points scorer.
"I've had a few problems, but for Ireland and at Northampton in the Heineken Cup it didn't come into it. But the most important thing for me is the team.
"I play for the enjoyment and the love of the game and I am just proud to be a Munster man."
