But the full house crowd were kept on tenterhooks right to the bitter end before Quinlan ended a period of Munster pressure to grab his side's fourth try.
Two first half tries from Denis Leamy had the home side 23-13 up at the break and things looked good when Barry Murphy raced in for try number three in the 48th minute. However Cardiff were never going to lie down and have their bellies tickled and try from replacement Mark Lewis left just one score separating the sides.
And Munster looked to be in trouble when Cardiff bust their defence in 65th minute and looked certain to score only for Jamie Robinson to spill a pass with a clear run to the sticks.
Munster held their composure and set siege to the Blues line as they went looking not just for the bonus but the score that would secure this victory. It came from Quinlan and Munster face into Christmas top of Pool Four.