Grace shot 3-under-par 69 in the final round for a 72-hole total of 21-under 267, which was three strokes better than defending champion Nicolas Colsaerts, who was also 3-under Sunday.
Grace won the Joberg Open and Volvo Golf Champions in back-to-back weeks in January. He is the second European Tour player, joining Johan Edfors who turned the trick in 2006, to win three tournaments the season after advancing through qualifying school.
Grace took a three-stroke lead into the final round and never let Colsaerts get closer than two through Sunday's play. He had a birdie at the second hole but bogeyed the fourth hole.
That was his fourth bogey of the week and proved to the last one Sunday. He had back-to-back birdies at Nos. 6-7 -- where he was 8-under for the week -- and another at 12.