The rest of the day, he was all business.
The 29-year-old South African shot his second straight 6-under 66 to reach 17 under and take a two-shot lead over Hunter Mahan after the third round of the Houston Open.
Carl Pettersson (67) and Brian Davis (69) were three strokes back at 14 under. James Driscoll (71) was alone at 12 under. Defending champion Phil Mickelson (70), Keegan Bradley (69) and Ryan Palmer (66) were 11 under.
"It's a great leaderboard behind me," Oosthuizen said. "It's going to be tough, but I feel like I'm ready for it."
Oosthuizen shook off two early bogeys on a sunny, windy afternoon at Redstone. He reeled off four straight birdies on the back nine, and in the midst of his streak, Oosthuizen enjoyed some of the natural scenery.
"It was such a beautiful back nine, really, with the weather and the sun dropping," Oosthuizen said. "Such a nice place out there, which was good, and (I) just felt when we turned on 15, I was playing down the sun and the course looked spectacular."
Mahan had a 65, which included four birdie putts of at least 23 feet. He sank a 23-footer on No. 5, a 34-footer on No. 6, and 28-footers on Nos. 10 and 14.
"That was a nice stretch there," Mahan said. "It easily could've gone through there even, instead of a couple under like I did."
Mahan doesn't feel quite as locked in as he did when he won the Match Play Championship earlier this year, but he still feels confident heading to next week's Masters. But Mahan has three top-10 finishes in Houston since 2007, and never considered bypassing this week's event to get to Augusta early.
"I thought about it for about a second," Mahan said. "But this is a place I've played well at, so I want to play well here and try to win here. I really didn't want to pass this tournament up. Augusta will take care of itself."
Three-time major champion Ernie Els, who must win to qualify for the Masters next week, was in a group at 8 under. Els hasn't missed the Masters since 1993 and knew that his chances of winning Sunday are remote.
"I needed to get to 10 or 11 under to really have a shot," Els said. "I need a 62 or 63. It's tough to do on a Sunday, but you might as well give it a go."
The tournament's schedule was pushed back by a thunderstorm Thursday, and 70 players resumed their second rounds Saturday morning.
Oosthuizen completed a 66 to move to 11 under, one behind second-round leader Jeff Maggert. Oosthuizen started his third round with a tee shot into a fairway bunker, leading to a bogey, then misjudged the wind off the tee on No. 2 and bogeyed again.
The 2010 British Open winner sank an 11-foot birdie putt on No. 6 to get rolling, then made birdies at Nos. 8 and 9 to make the turn at 12 under.
"After that, I felt really comfortable," Oosthuizen said. "I made really good swings after that."
Ninety players made the 36-hole cut at 2 under or better. It was the most players to survive the 36-hole cut in a non-major since 91 made it at the 1981 Travelers Championship.
Another cut was made after the third round, leaving 70 players in the field for Sunday.
Mickelson shot a 65 in the final round last year to win by three strokes, and he the course is ripe for someone to go very low again this year.
"I'll be going after it, really firing at pins and putting aggressively and having them go in at a little more pace," Mickelson said. "I think there's a really hot round out there."
Maggert missed five straight cuts coming into this week. Playing in calm, cloudy conditions on Saturday morning, Maggert finished his second straight 66 to surge to 12 under. He faded to a 76 in the afternoon to drop to 8 under.
Fred Couples, who played at the University of Houston and won on the Champions Tour last week, made the 36-hole cut in Houston for the 19th consecutive time. He shot a 71 in the third round and was 5 under.
Former President George H.W. Bush and wife Barbara were in the gallery in the afternoon, traveling between holes on a golf cart. The Bushes live in Houston and frequently attend sporting events around the city.