The 41-year-old McGinley played a near-flawless round with birdies at each of the four par-5s for a one-shot lead over Robert Karlsson. Marcus Fraser was another shot back in third at the 7,320-yard West Course, which was hard and bouncy after a recent dry spell.
Charl Schwartzel, Daniek Vancsik and Garry Houston shot 4-under 68s.
McGinley said his round was his best since an opening-round 67 at last years British Open.
I struggled most of this year with poor or medium first rounds, he said. But its a long way from leading now to winning on Sunday night. The Ryder Cup is not on the horizon. Its in the future. I have got to have a heck of a summer to make it.
McGinley, currently 32nd on the European points list and well out of the top 5 that qualify, has played on the last three European teams and had accepted an offer from Nick Faldo to be a vice-captain on this years team. He then backed out, saying hed like to qualify as a player.
Im not ready to be a back room staffer, he said. I dont feel Im ready for that role yet. In the future I hope Ill get to do those things.
Many players had trouble in the dry conditions'a departure from the soggy course of recent years. Karlsson, however, liked it just fine.
I putted really well, very well and I kept the ball in play, he said. Whenever I had a bit of a problem I tried to play sensibly.
Ernie Els is looking for his first win at this event after seven World Match Play titles on the same course, but struggled to a 3-over 75. Darren Clarke and defending champion Anders Hansen also shot 75s, Justin Rose shot 76 and Lee Westwood 77.
Four players'David Howell, Graeme McDowell, Nick Dougherty and Miguel-Angel Jimenez'were tied at 70. Paul Casey shot 71 after a double-bogey seven on the long 17th.
Three-time champion Colin Montgomerie double-bogeyed the short second hole and bogeyed the third, before battling back for a 73, and U.S. Open champion Angel Cabrera opened with five successive bogeys before rallying to shoot 73.