US Open champion Rory McIlroy birdied three of the last five holes in deteriorating weather to join Keegan Bradley in a tie for the lead after Tuesday's opening round of the end-of-season PGA Grand Slam of Golf in Bermuda.

The 22-year-old Northern Irishman battled strengthening winds and a torrential downpour to fire a 4-under-par 67 at Port Royal Golf Course in Southampton.

"I finished really, really well," McIlroy told reporters after taking joint control of the two-round stroke-play event which traditionally brings together the winners of the year's four majors. "I gave myself so many chances on the front nine and didn't really make anything but I started to hole a lot of putts on the back nine. It was a bonus to par 16 and birdie 17 in that bad weather, so I made up a few shots there."

American Bradley, who won his first major title at the PGA Championship in August, had seized early control with a sizzling front nine of 6-under 30 but lost ground with two bogeys after the turn to be caught by McIlroy.

South African Charl Schwartzel, the Masters champion, also struggled over the closing stretch on the way to a 74 while Northern Ireland's Darren Clarke, winner of this year's British Open, battled to a 77.

Bradley, who became the first player to win a major title using a long putter with his PGA Championship victory in a playoff at Atlanta Athletic Club, made a red-hot start highlighted by two eagles in his first seven holes.

"Two of the best shots I hit all year really, right at the pin the whole time," the 25-year-old said of his stunning six-irons into the green to set up tap-in eagle putts at the par-5 second and the par-5 seventh. "It was a great day. I got off to a really good start and I kind of slowed down on the back (nine), but still played very well. It was still a lot of fun."