Scotland's Jamieson, whose only European Tour victory came at the 2012 Nelson Mandela Championship, fired a bogey-free, five-under-par round of 67 to surge to the top of the leaderboard on -8.
The 33-year-old was much better on the greens as he made five birdies, opening up a one-shot lead from Frenchman Victor Dubuisson in second, and the Glaswegian is looking forward to Sunday's test.
"It's exciting. I'm in a good position, tomorrow will be a new challenge," Jamieson said. "Still, an awful long way to go, but if I can do what I did today, I'll be in with a good shout. It would be the biggest moment of my career, I'll be well aware of that tomorrow. I've got to see if I can step up to the challenge."
South African Branden Grace and Germany's two-time major winner Martin Kaymer are in a two-way share of third on -5, three strokes off the pace after carding rounds of 68 and 69 respectively.
Italian Francesco Molinari carding a sensational seven-under-par 65 - the best score of the day - to jump into a share of fifth on -3 alongside South African Haydn Porteous.