O'Gara kicked three in a row in the space of seven minutes and Munster extended the lead and looked to be set fair for victory when David Wallace was heaved over in the 66th minute after a period of intense Munster pressure. O'Gara added the extras and Munster were nine points clear.
However Glasgow were far from finished and DTH Van Der Merwe scored under the posts three minutes later. Ruaridh Jackson added the conversion and then slotted a driop goal to give Warriors the lead with five minutes remaining.
Munster came looking for the score to settle it and should have had it when a backline move ended with a scoring pass deliberately knocked out of Johne Murphy's reach. It earned Bernardo Stortoni a deserved yellow card.
It also presented O'Gara with a difficult penalty kick but as one expects, when the chips are down, the Munster out-half dissected the posts to snatch the spoils.
Munster: P Warwick; D Hurley, K Earls, L Mafi, J Murphy; R O'Gara, P Stringer; D Hurley, D Varley, J Hayes; D O'Callaghan, M O'Driscoll, J Coughlan, D Wallace, D Leamy capt. Replacements: M Sherry, D Kilcoyne, P Borlase, D Ryan, N Ronan, T O'Leary, T Gleeson, B Murphy.
Glasgow Warriors: B Stortoni; A Dunbar, M Evans, P Murchie, DTH Van Der Merwe; R Jackson, C Gregor; R Grant, D Hall, M Low; R Gray, A Kellock capt; R Harley, J Barclay, J Beattie. Replacements: P McArthur, K Tkackuk, J Welash, A Muldowney, R Wilson, H Pyrgos, D McCall, P Horne.