McIlroy birdied the tenth, but a bogey on the next meant his pursuit of Donald was all but over.
The tournament contest was anything but, though. Quiros had five birdies in the first seven, but also two bogeys and by covering the same stretch in five under Lawrie moved level on 17 under par.
They were four clear of Donald and Swede Peter Hanson.
Lawrie, who in March ended nine years without a win, rounded off a superb front nine 31 with a par four - and it took him ahead as Quiros was bunkered off the tee and had his fourth bogey.
Hanson was far from out of it after three successive birdies around the turn lifted him to 14 under, only three back.
Lawrie still led by one with seven to play, but went from rough to sand on the 476 yard 12th and his bogey dropped him alongside Quiros, while Hanson was two behind with four to play.
McIlroy remained nine under with two left, with Donald having six pars in a row to stay fourth on 13 under.