The 2010 Open champion established a two-shot lead after a brilliant 11-under-par 62 and has a quartet of fellow South Africans, including two-time US Open winner Retief Goosen, as his nearest title rivals.
However, Alastair Forsyth and Craig Lee are also in the hunt with two rounds to go in the opening event of the 2012 European Tour campaign.
Forsyth shot a flawless 66 in his second round to sit just four shots behind Oosthuizen on 135, the same mark Lee is on after a 67 that matched his fellow Scot’s seven-birdie haul.
A two-time European Tour winner, Forsyth lost his card at the end of 2010 and failed to regain it last season before missing the four-round cut in last month’s Qualifying School in Spain.
However, the 35-year-old Glaswegian reckons he is starting to reap some reward from swing changes he has been making since linking up with Stuart Kerr, the Strathaven club professional, in September.
“It’s nice to be playing some good stuff – the first time in quite a while,” said Forsyth, who finished 140th in last year’s Race to Dubai. “I’ve had two very steady rounds, making a lot of birdie chances. I’ve holed a few but also missed a few. Birdies have been the order of the day as the course is short and the wind hasn’t blown yet.
“I’ve worked on changing a couple of things recently, including my grip. That has been awkward, but I’m hitting the ball more consistently and long may it continue.”
Forsyth’s seven birdies came in two bursts - four in a row from the fourth then three on the spin from the 15th. In two rounds, he has dropped just one shot.
Lee has bagged 14 birdies over the same stretch to secure a cheque in his first event back on the main circuit after graduating from the Challenge Tour last season. “I think when my clubs got lost [in transit from London] they put someone else’s putter in the bag as I’m holing lots of putts this week,” joked the 34-year-old from Stirling.
“However, I only hit six fairways today, which is disappointing as there are lot of rescues and 3-woods off the tees here.”
Steven O’Hara, fourth in this event 12 months ago, is lying joint-50th after a second successive 70, while David Drysdale (69) and Alan McLean (71) also made the cut on 141. However, a dropped shot at his final hole proved costly for Lloyd Saltman. The Archerfield Links player got to five-under at one point but a 69 for 142 saw him miss out by a single shot.
Fifer George Murray also made an early exit after a 72 for 144, one less than Raymond Russell following his 74.
Oosthuizen began the day five shots off the pace, but carded nine birdies and an eagle to move to the top of the leaderboard on 15-under.
Overnight leader Thomas Aiken had to settle for a four-under 69 to lie on 13-under with Goosen (68), Tjaart Van Der Walt (64) and Jaco Ahlers (68). “I was aggressive on the putter,” said Oosthuizen.
“I went about six foot past a few times and I had to make those for par.”
On his eagle-2 on the sixth, where he had a double bogey in round one, he added: “It was a lot of concentration on the tee shot because I hit the 3-wood in the bush yesterday.
“It was a 3-wood again off the tee and I didn’t want to take any other club because I wanted to show myself that I can do it, because if I’d taken something else then the next day I would probably have a 3-wood again.”