Beginning his round on the back nine first, the recently-turned 38-year-old Scot faltered with early bogies at his third and seventh holes of the day, but quickly rebounded with four birdies, including three in a row at Nos. 4, 5 and 6, to end at 10-under-par 132.
He leads by two shots over Englands Anthony Wall ' who shot his second consecutive round of 67 Friday ' and by three over several others, including Barry Lane (67), Thomas Levet (67), Fredrik Henge (70) and Thomas Bjorn (69).
While Henge and Bjorn have each played strong golf through 36 holes at the Fota Island course, they could have been closer to Montgomeries lead entering the weekend.
Henge succumbed to the blustery conditions of Fota Island, dropping two of his last four holes to end at minus-seven.
Bjorn was tied for the lead at 10-under, but withered down the stretch as well, bogeying three of his closing four holes.
I played all right but my poor shots were very poor indeed, said the Dane following his round. I had a bad start and a poor finish although I played some nice stuff in between.
Monty, on the other hand, flourished at the end.
On losing the lead, it was important I didnt panic, he said, so I concentrated on what I was doing yesterday and I played the back nine in difficult conditions very well.
In a lot of ways that was a better round than yesterdays 63 because of the way I started. The wind got worse as the morning progressed and the pin positions were tougher. I think it was two shots at least more difficult, so Im pleased I got back to two ahead again.
Young Adam Scott and former British Open champion Paul Lawrie are no doubt pleased with their play entering the weekend as well.
Lawrie fired a beautiful round of 66 to reach the 5-under mark, while Scott backed up an opening round of 68 with 69 to end at the same score.
Spaniards Jose Maria Olazabal (75) and Seve Ballesteros (73) might not be overly satisfied with the week, however. Both missed the cut.
Full-field scores from the Murphy's Irish Open