The South African completed a 3-under-par 69 in the rain-delayed third round, then closed with 68 for a three-stroke victory over Scotland’s Stephen Gallacher.
“I was a little surprised to win here after that,” Oosthuizen said. “I thought I would be a lot more tired. My golf was a bit up and down in the morning at the end of the third round, but I settled down and played well later.”
The 2010 British Open champion finished at 17-under 271 on Kuala Lumpur Golf and Country Club’s West Course.
Gallacher shot 70. American David Lipsky also closed with 70 to tie for third at 12-under with Spain’s Rafael Cabrera-Bello and England’s Danny Willett. Cabrera-Bello and Willett shot 71.
The tournament was sanctioned by the European and Asian tours.
CHAMPIONS TOUR: In Lutz, Fla., Michael Allen won the Encompass Insurance Pro-Am for his second Champions Tour title, closing with 3-under-par 68 for a three-stroke victory over Kenny Perry.
Allen finished the three-day event at 12- under. He took a five-shot advantage into the final round, tying the tournament record for the largest 36-hole margin.
Allen bogeyed Nos. 3 and 4 at TPC Tampa Bay to cut his lead to one, but rebounded with birdies on two of the next three holes. He extended his advantage to four shots with birdies on 12 and 14.
Isao Aoki (1996) and Bruce Fleisher (2000) also took five-stroke leads into the final round of the tournament. Aoki wound up tied for eighth, while Fleisher won by four shots.
Perry eagled the par-4 first hole and par-5 12th during a round of 65. It was the fifth time in the event’s history that a player had a pair of eagles in a round.
Allen also won the 2009 Senior PGA Championship. He had gone winless in 40 consecutive Champions Tour events since then.
The 63-year-old Fleisher, who led after the first round, shot 74 to finish at 4-over.
Peter Senior was third at 7-under after shooting 67.
One of Perry’s playing partners, Corey Pavin, also had an eagle on 12. Pavin shot 70 and ended up fourth at 5-under.
Kirk Triplett had 72 to tie for eighth at 2- under in his first start on the tour.
NATIONWIDE TOUR: In Hayward, Calif., former Stanford player Alex Aragon won the TPC Stonebrae Championship for his first Nationwide Tour title, closing with 4-under-par 66 for a one-stroke victory over Matt Harmon, Duffy Waldorf and Paul Haley II.
Aragon had a 10-under 270 total and earned $108,000.
Harmon finished with 61, and Waldorf and Haley shot 68.