Kenneth Ferrie carded his second straight round of 4-under 68 to take second place at minus-8. Pierre Fulke and Ricardo Gonzalez share third place at seven-under-par 137. Paul Casey and Brett Rumford each shot 4 under rounds of 70 and are tied for fifth place at minus-6.
The three courses in use for the first three rounds this week are the Old Course at St. Andrews Golf Club, Carnoustie Golf Club and Kingsbarns Golf Links. The final round will be played at St. Andrews.
Montgomerie, who played St. Andrews on Friday, was on fire at the start of his round. The Scotsman sank a 10-foot birdie putt on the first and came right back with another 10-footer for birdie on No. 2.
The 42-year-old made it three straight to open his round as he birdied the par-3 third after his tee shot stopped within 2 feet of the cup. After a par on the fourth, Montgomerie ran home a 40-foot eagle putt on the par-5 fifth. He answered with a birdie on six to get to minus-8.
Montgomerie cooled off from there, parring seven straight holes around the turn and two-putting for birdie on the par-5 14th. Montgomerie closed with four straight pars to end at minus-9.
'I'm comfortable around this course in any condition at this stage, from the first shot to the last shot,' Montgomerie said. 'I'm very comfortable with knowing what to do here. We can play chess with this course right now and we can get it round and that is what we did today.'
Ferrie played the back nine at Carnoustie first. He ran in a birdie try on the 11th and made it two straight as his birdie putt on the 12th found the bottom of the up.
The Englishman birdied the par-3 13th to move to 7 under and sank his fourth straight birdie on the 14th. Ferrie's birdie run ended with a bogey at the 15th.
Ferrie dropped another stroke on the 18th, his ninth. Around the turn, he reclaimed those lost strokes with birdies on the fifth and seventh. He parred his final two holes to end in second place.
'All round I am playing well,' said Ferrie. 'I have been doing extra work on my putting and it is paying dividends. It is nice to be in touch at this stage.'
Alessandro Tadini, who shared the first-round lead with Rich Beem and David Howell, carded an even-par 72. He shares seventh place with Brian Davis, Peter Hedblom and Terry Pilkadaris at 5-under-par 139.
Beem is one stroke further back at minus-4 after a 73 at St. Andrews. Howell, who also played the Old Course, is one shot behind Beem at 3-under-par 141 after carding a 2-over 74.
Defending champion Stephen Gallacher is in danger of missing the cut, which comes following the third round. Gallacher shot 74-73 the first two days and stands in a tie for 103rd at 3-over-par 147.