Set up by a birdie-birdie-eagle salvo on the back nine, the South African added a 65 to his opening 64 on Thursday for an 11-under aggregate to lead by two shots from American Collin Morikawa, with his compatriot, Jordan Spieth, one further back.
Dustin Johnson, the world No 1, is also sitting in the top five on the Kent coast, but, on the evidence so far, Oosthuizen looks in the mood to finally go one better after finishing runner-up in the last two majors and six in total since his St Andrews success in this event 11 years ago.
“Yeah, played really solid today and in good position for the weekend,” said the Mossel Bay man, who has dropped just one shot in 36 holes in claiming that tournament record from Nick Faldo (1992) and Brandt Snedeker (2012) after they both reached the same point on 130.
A “spinny little lob wedge from a perfect distance” at the 12th sparked the leader’s burst on the inward journey before he then rolled in a 15-footer to also birdie the next hole. When he then hit a “good solid 4-iron” to 25 feet at the 14th and holed that as well, he had suddenly burst three shots clear.
A “horrible mental mistake” led to a bogey at the par-3 16th before he then “had a lot of work to do” to save par at the penultimate hole, but, overall, it was impressive stuff from the 38-year-old.
“To have any record at the Open or part of any record at the Open is always very special,” he said. “Around this golf course, a lot of things can happen. I don't think you want to think too much of winning on a links course until you get to that 18th green, and hopefully you have a lead.”
On that run of close shaves, he added: “I just need to pull it through and see if I can go one better on this weekend. The game is good, but I know it's a really good leaderboard. I have to play good golf this weekend if I want to come out first.”
Admitting he’d benefited hugely from a links warm up in last week’s Scottish Open in East Lothian, Morikawa had earlier set the clubhouse target on the back of a brilliant 64, the day’s best score along with Argentina’s Emiliano Grillo.
The 2020 US PGA champion birdied the first, fifth, eight and ninth to be out in 31. When he then added further gains at the 11th, 12th and 14th, he was in with a chance of joining Branden Grace as the only players to post 62 in a men’s major.
That wasn’t to be as the 15th delivered a first bogey of the day before he then saw a great birdie chance go begging at the last, but it’s so far, so good for the Californian as he bids to emulate 2013 winner Ben Curtis in making his Open debut a winning one here.
Talking about how he’d already achieved that with his US PGA title triumph at Harding Park in San Francisco last year, Morikawa said: I had seen every single guy before, I had played with every single guy, and that doesn't make anything different.
“It's just the stage that we're on, more media, more spectators, more people around. But that's everything outside that I could control.
“For me, it's just let's go figure out this golf course Monday through Wednesday like I have been the past couple years and figure out what I need to do to play well.”
A bit like Brooks Koepka, who has four to his name, you get the feeling that Morikawa could be a major machine. “Every single one is important to me and I want to create lifetime memories,” he said of the game’s biggest events.
Taking up where he’d left off when opening with a 65, Spieth started birdie-birdie before moving to four-under for the day with gains at the 10th and 12th. It was a disappointment for the Texan, though, that he then covered the closing stretch in one-over, especially as Oosthuizen had moved up a gear over the same holes.
“Those last six holes were kind of frustrating,” admitted Spieth after signing for his 67. “I think I need to bring more food on the golf course tomorrow. I got really just in a weird headspace, like fatigued there on like the 13th green as we were waiting and hitting putts.
“I just didn't stay focused like I was early in the round. Wasn't very sharp. It's an easy solution for tomorrow. But the finish on 18 probably securing a second to last group on a Sunday is a good position to be in, but I was eyeing a number lower this afternoon than what I finished at.”
The course has really dried out from earlier in the week, to the extent that Spieth reckons a change of tactics might be required on some tees as the notorious adverse cambers on these fairways start to have a bigger impact on the proceedings.
“I might look into what clubs I'm hitting off tees,” he said. “I've been able to hit driver a lot around this course, and I'm not sure if that'll stay the same or if I'll look to make sure we're positioning ourselves in the fairway more. For me personally it's just keep doing what I've been doing and then try and make a few more putts.”
Johnson, who finished joint-second here in 2011, signed for seven birdies to sit alongside fellow American Scottie Scheffler and South African Dylan Frittelli, with US Open champion Jon Rahm on five-under and defending champion Shane Lowry on four-under after covering his final 13 holes in five-under.
On a day when compatriot Marcel Siem shot a second successive 67 to sit handily-placed on six-under, Germany’s Matthias Schmid joined leader Oosthuizen in re-writing the record books with a 65 - the lowest by an amateur in the event.