Wales' Stephen Jones who, along with Jonny Wilkinson, is O'Gara's biggest challenger for a Lions' Test team spot this June, finished second with 22 successes for a 57-point return.
The award is some consolation to O'Gara, whose attempted clearance was charged down by prop Gethin Jenkins to set up Wales' 32-20 victory.
O'Gara told told Irish rugby website www.irishrugby.ie: "The charge-down try was a killer. I didn't see him and that made it 10-3, after we had started the game well.
"We were chasing the game from then on, but every time we got into a good position we gave away a penalty.
"But the better team won on the day."