Montgomerie broke clear of a battle for the lead midway through his round to edge clear by one over Scott Dunlap and by two over Bernhard Langer and Gene Sauers.
Montgomerie who is enjoying a great season on the Champions Tour with his victory at the Senior PGA Championship and numerous other finishes in the top ten may yet find some consolation for his near misses in two US Opens on the regular tour.
When asked if it felt like a US Open Montgomerie was quick to respond. "Very much so. The nerves are there, the course setup is as good as you could play a proper U.S. Open on this course, never mind the Senior Open. It's a fantastic setup, run superbly well. Yeah, it feels like a major, it really does.
"You know, for people that say that these aren't real major championships, well, you come and compete then. You come and try it, you know? You come and try this. It's bloody difficult, I tell you. I'm just delighted to be in this position on Friday evening."
Langer is still the man who Montgomerie is fearing most, but the German is well aware of the demands of this layout. "Yeah, when I played my practice rounds I said this was one of the hardest courses I ever played.
"The USGA ranked it third or second hardest golf course in America from the slope rating, and I can certainly see that."
Vijay Singh, playing his first US Senior Open, is very much in contention at 2 under and just four from the lead.
Peter Senior (33rd) and Steve Elkington (40th) are the only two Australians to make the cut with Peter Fowler missing out on a start at the weekend.