Montgomerie had trailed overnight leader David Frost by three shots after the opening day’s play at Constance Belle Mare Plage in Mauritius, but he seized the initiative with a dominant display on day two, the undoubted highlight his eight iron into the cup from 164 yards on the penultimate hole.
That ace, allied to five birdies in a flawless performance, moved Montgomerie to 12 under par, four shots clear of Frost and the latter's fellow South African Chris Williams.
Victory on the final day in Mauritius would set the seal on another stunning season for Montgomerie, who is yet to finish outside the top three in four appearances on the European Senior Tour this term.
He said: “When you drive the ball well on this course and keep it in play from the tee, you’re likely to have a good day out there – especially as my iron play is my strength.
"I think I hit 16 greens out of 18 today and managed to take a few birdie chances, then of course the 17th was a bit of a bonus.
“Normally I hit my eight iron 158 yards, so I was on the limit, but the wind was helping us slightly. I struck it very nicely, then it got a kindly bounce and started tracking towards the hole, so at that point I started getting a little excited. You always hope it’s going to drop in, but of course it rarely does, so it was very nice to see it disappear from view.
“That finish sets me up very nicely for tomorrow. I’ve given myself every chance of finishing the season on a high note and that’s what we’ll try to do. But it won’t be easy, we all know from past experience David is a great competitor and he loves it round here, so I’ll have to play very well to win.”
Despite a stiffening breeze, Frost had again looked in control of his game until the 15th hole, where his tee shot found the water. The resulting double bogey undid some of his good work on the front nine, which he covered in 34.
A back nine of 37 for a round of 71 and an eight-under-par aggregate total is not terminal to his hopes of securing a third victory in the €420,000 tournament, but the 56-year-old knows he will need to be at the top of his game on the final day if he is to catch Montgomerie.
Frost, whose opening round of 64 three years ago had set the course record, said: “I hit a couple of loose shots on the way in.
"Maybe I got a little conservative but it’s difficult to concentrate fully in the heat. I got a little light-headed and a little dehydrated, so that’s probably cost me in the end, but I’m still in with a good chance on the final day.
“I’m probably going to have to go low, but you never know what can happen in golf. I’ve got less to fear and nothing to lose, so I’ll set out aggressively and try to put some pressure on.”
Williams will partner Montgomerie in the final group after carding his second successive round of 68.
After three birdies on the front nine, he added a further gain on the 13th to move into contention to claim his first title for four years.
Barry Lane also put himself in position to win the season finale for the first time, having finished runner-up last year and in 2012.
The Englishman, currently third on the Senior Tour Order of Merit, rounded off a 65 in fine style, chipping in on the last to climb to fourth place on seven under par.
He said: “It was very tricky in the wind, so I’m delighted with a 65. I broke my driver in the pro-am and drove the ball poorly yesterday, but I trusted myself a little more off the tee today, and it paid off.
"I also putted a lot better today, and the chip in on the last was a lovely way to finish. I’ve given myself an outside chance, but at least I’ll have something to play for tomorrow.”