Quiros, who made five birdies on the front nine, totaled 16-under 200 at Doha Golf Course.
"I have been telling people that I am not just a long hitter," Quiros said. "It has been a lucky week for me. I could see this score coming. I can't even remember when was the last time I won."
"I started well, but then fell asleep on the fifth green when I made a four-putt. It was a mental error, lost my
concentration," Oosthuizen said. "In a way I think one behind is a good spot. Three or four
ahead, everyone really is thinking you have to win. One behind is nice and I'm happy with that."
Garcia had a bogey on the last hole.
"It is disappointing because I hit such a good tee shot on the last and just got a bit of a mud ball," Garcia said. "Hit a good second. The ball just went exactly the opposite way I wanted to go. It is one of those things."
Information from Reuters and The Associated Press was used in this report.