McGinley was eight shots behind the overnight leader, the Spaniard Juan Carlos Pinero, when he began but he sank 11 birdies to finish on 269, 19 under par, to beat Pinero and David Lynn by one shot.
Pinero was level with the 29-year-old Irishman with two holes to play but three-putted the short 17th and then just missed a 10-foot putt on the last which would have forced a play-off.
The Irishman has finished second four times in previous Tour events and said: "I have been so close so often I knew my time had to come. I know how Pinero must feel after three-putting the 17th and my heart goes out to him. He led the field by three shots at the start today and then shot a one-under 71. He didn't lose the tournament, I won it.
"I am over the first hurdle. The first win is now out of my mind. It has been nagging me for quite a while and to do it in this style is fantastic."
His 10-under-par 62 was forged when he birdied seven of the first eight holes and had four more birdies coming home. His 11th of the day came at the 377-yard 18th where he hit a "perfect sandwich" to three feet and holed the putt.
Pinero began with a birdie but dropped shorts at the fourth and fifth. Fighting back, he levelled with McGinley at 19 under but then came the fatal three putts at the 17th.
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