Starting from the 10th, Mickelson, who lost out to France's Gregory Havret in a play-off in this event 12 months ago, opened with three pars before a bogey on the 13th, the only par five on the back nine and usually a good birdie opportunity.
Scotsman Lawrie is an automatic entry next week following his victory at Carnoustie in 1999 but he is looking for his first European Tour title since 2002. He did his cause a power of good by picking up two birdies this morning to lie six-under alongside Henrik Stenson.
The Swede reached the turn in 35 with nine straight pars. Then three birdies in a row took the Ryder Cup star to seven under par before he dropped his first shot of the day.
World No6 Ernie Els was also on the up. The South African, playing in the group ahead of Mickelson, carded five birdies in 10 holes to improve to three-under.
Els, twice a winner at Loch Lomond and third last year, dropped two shots in his last three holes last night and moaned: "Right now I should not even play tomorrow, that's how I feel."
But he birdied the 10th, 13th, 14th and 15th and, after a bogey at the 18th, also picked up a shot on the second.