K.J. Choi, the second-round leader, managed a 2-under 70. He slipped into a tie for second place at 15-under-par 201 with Richard Green (66).
Australian Nick O'Hern shared the low round of the day as he fired an 8-under 64. That helped him jump into a tie for fourth place at minus-14. He was joined there by Gavin Flint (66) and Francesco Molinari (66). Australian Craig Parry was joined by 1995 champion Fred Couples at 13-under-par 203.
Stadler opened with a birdie on the first to remain two behind Choi, who also birdied No. 1. Choi extended his lead to three as he eagled the par-five third, while Stadler birdied the same hole.
Choi tripped to a bogey on the fourth, then Stadler closed within one as he birdied the fifth at The Vines Resort & Country Club. Each man birdied the sixth as Choi maintained his one-shot cushion.
However, Choi faltered to a double bogey on eight to slip one behind his playing partner, Stadler. Choi moved back into a share of the lead at minus-15 with a birdie at the ninth.
Stadler, who is playing this week on a sponsor's exemption, birdied the 10th as Choi bogeyed the same hole. The 26-year-old Stadler bogeyed No. 11 to slip back to 15 under, but he still led by one over Choi.
Green, playing one group in front of Stadler, made the turn at 11 under with two front-nine birdies. On the back nine, Green birdied the 10th, 11th, 14th and closed with a birdie on No. 18 to tie Stadler at 15 under.
'It was a nice Saturday's round of golf to put yourself in position for Sunday and I was quite pleased with the way I played,' Green said.
Stadler, who parred six straight from the 12th, eagled the par-5 18th for the second straight round to move two clear of the field after three rounds.
On Sunday, Stadler will go for his first European Tour title. He has won twice on the Nationwide Tour in the United States, and also claimed the 2005 Centenary Argentine Open.
'The scores seem to be pretty low today,' said Stadler. 'Everybody was getting up there 13-, 14-, 15 under. I expect more of the same tomorrow. So as far ahead as I can get, the better I get.'
Choi, who parred holes 11 to 17, birdied the last to share second place with Green.
Paul Casey, a five-time winner on the European Tour, posted a 5-under 67. That helped him move into a share of ninth at 12-under-par 204 with fellow Englishman Ross Fisher.
Adam Scott, who won this event last year when it was played at Pine Valley Golf Resort and Country Club in Beijing, China, shot 70 on Saturday. He is tied for 11th at minus-11 with Chris Campbell (67), David Diaz (64), Stephen Leaney (69), Ian Poulter (69) and Gary Simpson (67).