Green sank a six-foot putt at the par-five 17th for birdie -- his eighth of the day at the par-71 Meadow Brook Club -- to grab the outright lead at 12- under par. Needing a three at the 167-yard closing hole to tie the course record of 63, Green wound up missing a six-footer and bogeyed to complete a seven-under-par 64.
'My game is coming on,' said Green, who shared the runner-up spot at last month's Senior Players Championship, the final major of the 2002 season. 'It will be interesting in the next few weeks.'
Irwin, who took the lead Friday with an opening-round 64, shot a bogey-free 67 Saturday that could have been much better.
'That was probably one of my more exasperating rounds in a while,' said Irwin, who squandered a day in which he hit 13 of 14 fairways and 17 of 18 greens by taking 31 putts. 'I had 14 putts inside 15 feet and only made four of them.'
One of Irwin's misses came at the 17th, where he had a chance to move to 12- under but was off the mark on a five-foot birdie attempt.
'I think I could have put some space between myself and the field if I had just made some putts,' he said.
Irwin, who has posted a pair of wins this year to push his Senior Tour-leading total to 34 career victories, has won 23 of the 31 events he has led or been tied for the lead heading into the final round.
Morris Hatalsky carded a flawless 65 that included a downhill birdie putt from 25 feet at the 15th. He finished alone in third at 10-under 132.
Bruce Fleisher, a back-to-back winner on Long Island in 1999 and 2000, had a second-round 67 and was in fourth place at nine-under 133. Tom Purtzer and Mike Hill each shot 65 to finish at minus-eight.
Dale Douglass (67) and Howard Twitty (69) were next at seven-under, while Allen Doyle (68), Dana Quigley (68), Walter Hall (70) and Lee Trevino (70) rounded out the top-10 at six-under 136.
Quigley won the 1997 Long Island Classic after earning his way into the event as an open qualifier. Trevino captured this title in 1994 and '95.
Bobby Wadkins, the winner of this event last year in his first start on the Senior Tour, was eight strokes off the pace at three-under par.