Ireland\'s Padraig Harrington won the PGA Grand Slam of Golf on Wednesday, firing a four-under par 67 to beat US Open champion Webb Simpson by one stroke in the four-man, 36-hole event. Harrington, a three-time major winner, lost out in playoffs in this event in 2007 and 2008. His third attempt saw him playing as an alternate in the tournament designed for the year\'s four Grand Slam champions, filling in for British Open champion Ernie Els, who withdrew with a mild ankle sprain. Harrington birdied three straight on the back nine to pull away and finished with a nine-under total of 133 to claim the $600,000 first prize. Simpson posted a 67 without a bogey to finish second on 134. Masters champion Bubba Watson carded a 71 and former PGA Championship winner Keegan Bradley a 67 to share third on 139. Bradley, who won this event last year, was filling in for reigning PGA Championship title holder Rory McIlroy, who withdrew to play a European Tour event in China.