The 31-year-old was given his marching orders on the hour after upending Johnny Russell just outside the area, but Harry Redknapp's side went on to win the game regardless, thanks to Bobby Zamora's late goal.
O'Neil told Sky Sports News after the game: "I knew I was getting a red, I've never been sent off before.
"I did it for the best of the team at the time, thankfully it worked out. If he scores we go 1-0 down, maybe it helped out.
"This is the best way to go up if you can guarantee doing it. It's a fantastic day and I'm delighted for the fans and the owners."
QPR had one shot on goal during the entire game, which turned out to be the winning goal.