Garcia waited out a lengthy rain delay and finished his round in gathering darkness, but nonetheless turned in a solid performance to finish at 19-under-par 194, tying the tournament's three-round scoring record.
The Spaniard, seeking his ninth career PGA Tour win, entered the day with a one-stroke lead and ended it with a two-shot advantage over Henrik Stenson, who carded a 66 to end at minus-17 for sole possession of second place.
Steve Stricker notched an 18th-hole eagle to register an 8-under 63 and Graham DeLaet birdied five of the last seven holes for a 9-under 62 to finish 54 holes tied for third at 16-under 197.
Sharing fifth at minus-15 were Jason Dufner (66) and Roberto Castro (68).
With more bad weather forecast for Monday, final-round tee times have been moved up.