The Irish team and past legends gathered at Hillsborough Castle for a civic reception held to honour their Grand Slam victory yesterday.
However, O'Gara failed to take his hands out of his pockets when greeting the sovereign.
O'Gara's casual stance has horrified rugby fans who feel he showed complete disrespect for the monarch.
Coach Declan Kidney, as well as 1948 Grand Slam legends Jack Kyle and Jimmy Nelson, accompanied the players, as they met the queen and the Duke of Edinburgh.
Team captain Brian O'Driscoll had his hand over his mouth when watching O'Gara's royal encounter. Discussion websites were immediately rushed with comments from appalled Munster fans. "The Irish team were being congratulated by the queen and O'Gara stood with his hands in his pockets," said one fan. "Just wanted too express my disgust in his behaviour."
"Very dis-respectfull allright (sic)," said another in a thread entitled Ronan O'Gara ... Very Disrespectful.
While a number of fans said that they didn't believe that the outhalf should have acted any differently, others were outraged. "I agree ... ROG is a thundering disgrace," said one blogger.
"As a grown-up country you show respect to other countries leaders regardless as to how they attained that position," said another.
Ronan is reported to have chatted to the Queen about her grandson William, who he met on two previous Lions tours and that he found him "a lovely young man".
Pat Geraghty, a Munster Rugby representative defended O'Gara today saying: "I think that he spoke very well. I believe Ronan always acts in a correct and respectful manner. He always represents his country very well".
After the meeting yesterday, players spoke about how pleased they had been to meet royalty.
"The queen was lovely. It was very special," said Rory Best. "You know, in terms of special guests, you don't get better than that."
Stephen Ferris's girlfriend Lauren Hood revealed that she was worried about how her curtsey had gone, while Stephen joked: "Well, I asked her for a pint of Harp and a packet of crisps," he laughed.