Goosen had a disappointing 72

Two-time US Open champion Els completed a second-round 69 to move to five under par, one stroke better than defending champion Garcia.

But it was Roberts, known as the "Boss of the Moss" for his putting prowess, who led after adding a 68 to his opening 64 for a 10-under total.

He said: "I played as well as I did yesterday, but I didn't make quite as many putts.

"When I've won it's been on a real major run with the putter. I'm usually not going to beat anybody with ball-striking.

"I am going to do it with the blade. And it feels very good this week."

The 23-year-old Gossett birdied the final two holes for a 67.

Americans Chris Smith and Jerry Kelly shared third place, a stroke ahead of compatriot Stewart Cink and Argentina's Jose Coceres.

US Open champion Retief Goosen and world number two Phil Mickelson were among a group seven shots back.

Leading scores after day two of the Buick Classic:
(US unless stated)

10 under: Loren Roberts 64 68
9 under: David Gossett 66 67
7 under: Jerry Kelly 65 70, Chris Smith 66 69
6 under: Stewart Cink 67 69, Jose Coceres (Arg) 68 68
5 under: Shaun Micheel 69 68, Ian Leggatt (Can) 69 68, Bryce Molder 71 66, Jim Furyk (12), Ernie Els (Rsa) 68 69, Jim Furyk 68 69, Pat Perez 67 70
4 under: David Toms 70 68, Woody Austin 69 69, Brian Gay 68 70, Dudley Hart 73 65, Sergio Garcia (Spa) 68 70, Steve Elkington (Aus) 67 71, Cameron Beckman 73 65

3 under: Neal Lancaster 69 70, Hal Sutton 71 68, KJ Choi (SKor) 72 67, Phil Mickelson 69 70, Frank Nobilo (NZ) 69 70, Peter Lonard (Aus) 71 68, JJ Henry 71 68, Jim Carter 67 72, Retief Goosen (Rsa) 67 72, Scott Hoch 70 69, Len Mattiace 69 70, Phil Tataurangi (Nzl) 69 70, Mike Sposa 69 70.