The 32-year-old Scot went low at Luffness New, one of four courses where 480 players are vying for the final 24 spots in the year's third major championship, which begins at Muirfield on Thursday.
Course records were established at two other venues on Sunday, where the golfers were aided by near-perfect scoring conditions with no wind under overcast skies.
South Africa's Trevor Immelman, the runner-up in the Open de France back in May, shot a record 63 to tie for the lead in qualifying at North Berwick. The score was also posted by Irish amateur Colm Moriarty.
Fredrik Andersson of Sweden set the course record of 62 at Gullane No. 1.
Low scores were harder to come by at Dunbar, where 1999 European Ryder Cup captain Mark James, fellow Englishman Sam Walker, and Sweden's Patrick Sjoland turned in 65s for the lead at that course.
Some notables battling for spots in the British Open field were: at Luffness New, Americans Mark Brooks (68) and Jay Haas (72); at Gullane No. 1, Mark NcNulty (71) of Zimbabwe; at Dunbar, Australia's Steve Elkington (67) and South African David Frost (69); and at North Berwick, Sweden's Jarmo Sandelin (69), who won the European Tour's season-opening event in Taiwan.
Monday's second round will decide who will join the players who have already earned exemptions to compete at Muirfield.
Fifteen other players qualified for the championship after the Scottish Open was completed on Sunday.
Fredrik Jacobson of Sweden, who lost to Eduardo Romero in a playoff Sunday at Loch Lomond, was among seven players not already exempt who qualified through a special money list. The others were Roger Chapman, Bradley Dredge, Gary Evans, Darren Fichardt, Soren Hansen and Ian Poulter.
The top-eight finishers at the Scottish Open not already exempt also qualified for the Open: Warren Bennett, John Bickerton, Paul Casey, Marc Farry, Ricardo Gonzalez, Stephen Leaney, Jean-Francois Remesy and Jamie Spence, who came up big with birdies on three of his last five holes Sunday.
Full coverage of the 131st British Open