Scott, who last played at Loch Lomond in 2003, is currently ranked seventh in the world and 12th on the European Tour Order of Merit.
Eight players in the world's top 20 will be challenging the defending champion, Thomas Levet.
In addition to Mickelson and Scott, the field includes Ernie Els, Retief Goosen, Darren Clarke, Luke Donald, Miguel Angel Jimnez and Angel Cabrera.
Last year, Levet fired a final-round 8-under-par 63 to overtake Els and this year's U.S. Open champion Michael Campbell. Els won the title here in 2003.
Players will be playing for a purse of $3,500,645, with $602,962 going to the winner.
The Golf Channel will televise all four rounds live beginning Thursday at 9:30 a.m. ET.