McGinley began with an eagle at the par-5 second hole followed by a birdie at the third.
Later, he bogeyed the eighth but had a string of birdies from 12-15.
Orr made an eagle at the par-5 12th and four birdies.
"My season's been flat," McGinley said. "I've not played well enough and I need to do better."
"I've been playing pretty well lately, just not making enough putts," Orr said.
McGinley was the runner-up in 2008, while Orr is seeking his first victory in nine seasons.
Defending champion Darren Clarke joined Peter Lawrie, Jorge Campillo and Matthew Millar in a tie for third at 5-under 65.
Clarke shot 66 in each of the final two rounds last year and won by four strokes.
Copyright 2009 by United Press International.