O'Hara didn't have a bogey in the second round in moving to 11-under 133 after 36 holes. Merrick Bremner and Retief Goosen each also shot 68 Friday and are tied for second at 10-under.
Garth Mulroy (68 Friday) and Lyle Rowe (66) are in fourth at 9-under. Jbe Kruger, who was tied with O'Hara for the first-round lead, shot 1-under 71 Friday and is tied with Jean Hugo (69) at 8-under.
O'Hara, playing the back nine of the Serengeti Golf Club first Friday, had a birdie at the 11th hole and back-to-back birdies at 16 and 17. He got to 4-under on the round with a birdie at 2 and finished the day with seven consecutive pars.
Goosen had five birdies, including opening the round with back-to-back birdies and finishing with another at 18, against one bogey Friday.
Bremner was even after his first eight holes, despite a bogey at 12 and a double bogey at the 13th hole. He birdied No. 18 and had three more birdies on the front nine in getting to 10-under for the tournament.