Mark Murless finished at 12-under 198 while current Sunshine Tour Order of Merit leader Tim Clark is two shots further back at 10-under.
Sterne, who's best finish this season was second at the Graceland Challenge, carded his third straight round in the 60s. The 20-year-old used three birdies and an eagle on the par-5 16th to join the others atop the leaderboard.
'I'm just having a lot of fun out there,' he said. 'I missed a few makeable putts for birdie. But I'm not going to cry over spilled milk.'
The former South African Amateur champion, who turned pro only seven months ago, has posted six top-10 finishes in the 19 tournaments he has played on the Southern Africa Tour.
Kingston, who fired a 9-under 61 in the second round, had five birdies on the Wild Coast course Saturday but was dealt with some trouble with bogeys on the fifth and 15th for a round of 67.
'I started making mistakes on the back nine and got frustrated, especially after being in such a good position,' said Kingston, who hit an errant driver into the water at 16. 'It felt like I was making a mistake on every hole.'
Moore, the leader after round one, began the day with back-to-back birdies from the second. The 1996 South African Amateur Champion then bogeyed the par-three sixth before adding three more birdies for a round of 66.
Drummond was tied with Retief Goosen after three rounds of the Dimension Data Pro-Am last week before relinquishing the lead to the U.S. Open winner.
The Scot torched the front nine of the Wild Coast course Saturday with five birdies. However, the 27-year-old bogeyed three of the first five holes on the back nine.
Rose, currently third on the Sunshine Tour Order of Merit behind Clark and Goosen, had seven birdies and two bogeys for a 65.
'It's set up for a terrific finish,' said the Dunhill Championship winner. 'The guy who putts best is going to win.'
Full-field scores from the Nashua Masters