John Cook and David Edwards matched Montgomerie's 65 - the lowest score of the week so far - and tied three-time Open champion Hale Irwin for second place at 138. Irwin had his second straight 69.
Jack Nicklaus, at age 54 seeking his fifth Open title, birdied four holes on the front nine and hung on for a 70 to join Jeff Maggert (68) at 139. Two- time Open winner Curtis Strange, with a 70, held down a spot at 140, along with Steve Pate, South Africa's Ernie Els and Open first-timer Frank Nobilo. Pate shot a 66; Els and Nobilo, of New Zealand, came in with 71s.
Again yesterday, temperatures reached the mid-90s, and not even a breath of a breeze could be detected until late in the day, when thunderstorms forced the suspension of play just before 8 p.m. with 18 players remaining on the course.
The cut will not be determined until those players finish their second rounds, though the projection is 5-over 147.
Earlier in the week, the muggy conditions and Montgomerie, the No. 2 player on the European tour money list, hadn't been a good match. He needed to go to the medical tent after Tuesday's practice round to have fluids replaced intravenously.
He is getting used to the weather - yesterday he made an eagle, five birdies and one bogey.
"You never really cope with it 100 percent," he said. "The concentration level is difficult because the play is very slow, over five hours in that heat. With practice, it's six hours. I'm glad I could come back in 32 (on the back nine) under these conditions."
Most players have been leaving the driver in the bag on most of the par 4s and par 5s, but not Montgomerie. Taking advantage of his natural tendency from left to right, Montgomerie starts the ball over the left edge of the rough and fades it into the fairway.
"Let's hope it can continue," he said.
In a round filled with highlights, Montgomerie's biggest came at the 474- yard par-5 ninth hole, where he hit his second shot into a bunker fronting the green and blasted out and into the cup from 25 feet for an eagle. He finished the day by rolling in a 10-footer for a birdie at No. 18.
"That's about as good as I can do," Montgomerie said. "My goal at the start of the year was to get into contention in major championships. I missed the cut at the Masters, but that course doesn't suit my game. But this does, and I'm looking forward to the weekend."
Montgomerie wasn't the only one to shoot a low number yesterday. Cook and Edwards matched his figure, which tied an Open second-round record for lowest score in relation to par. In all, 29 players broke par yesterday, a figure largely attributed to a thunderstorm that struck Oakmont late Thursday night. Only nine subpar rounds were shot Thursday.
"I think the course was a little softer," Nicklaus said. "Hitting into the greens, you had a little bit more of a chance to stop the ball."
Nicklaus, who won his first major as a professional at the 1962 Open here, held his game together for the second straight day, although he admitted, "I didn't play as well as I did" on Thursday.
Beginning the day 1 shot off Tom Watson's first-round lead, Nicklaus birdied three of his first five holes to get to 5 under for the tournament. However, he bogeyed the sixth, seventh and 13th holes, picking up his only other birdie with a 10-foot putt at the par-3 eighth.
When it was over, the big news for Nicklaus was that he had made his first
cut in seven tournaments on the regular tour this season. And the bigger news was, "If I played a good round (today), I have a chance of winning the U.S. Open."
"I hope I have played my bad round of golf as far as hitting the ball," he said. "If I get myself in position on Sunday, I think I've got a shot to win."
He'll have company. Cook notched six birdies in a 65 that was posted three hours before Montgomerie completed his round. Edwards, who ranks 17th on the PGA tour money list this year, drained eight birdie putts, finishing shortly before play was halted. Irwin had an eagle and four birdies and 1-putted the first three greens to save par.
But, out of all of those, it is Montgomerie who has the best chance to make history, becoming the first European to win the Open in 24 years. The last non-American to walk away with the trophy was Australian David Graham at Merion in 1981.
"There is great significance" to winning the Open, said Montgomerie, who came close in 1992 when he finished third at Pebble Beach. "It would mean a lot to British golf to win, and I just happen to be in a position to do it."