Jason Dufner holds a two-shot lead at the halfway mark of the Crowne Plaza Invitational, with Greg Chalmers the best performing Australian.
Dufner's six-under second round of 64 on Friday saw him replace fellow American Zach Johnson at the top of the leaderboard.
Tied for second after Thursday's opening round of the US PGA Tour event, Dufner sunk six birdies on day two, including four in the space of five holes at the beginning of his back nine.
After teeing off on the 10th, the 35-year-old made birdie at the 1st, 2nd, 3rd and 5th, to go with the early strokes he picked up at 13 and 17.
A two-time winner on the Nationwide and PGA Tour respectively, Dufner is a man in form following his triumph at the Byron Nelson Championship last week.
He heads an American-dominated top half of the leaderboard at Colonial Golf Club, Texas, with Chalmers tied for 21st, and unlikely to challenge during the weekend.
The 38-year-old, a two-time Nationwide winner who is yet to bag a PGA Tour event, managed a one-under 69 on Friday to sit 10 shots off the pace.
Compatriots Marc Leishman, John Senden and Geoff Ogilvy are all even par for the tournament, tied for 30th.
And fellow Australian Aaron Baddeley is a shot worse off, in a share of 42nd place at one over.
A player with more realistic hopes of catching Dufner is first-round leader Johnson, who had opened with a 64 to set the pace on Thursday.
The 2007 Masters champion could only manage a three-under 67 a day later, to hold outright second going into Saturday's penultimate round.
The front-runners are followed by a two-way tie for third, with Bo Van Pelt and Tommy Gainey level at seven under.
Tom Gillis holds outright fifth at six under, while Ryan Palmer and Harris English share sixth at five under.
Anders Romero is one of the best-placed non-American players, the Argentine is tied for 12th at three under, alongside South Korean Charlie Wi and England's Greg Owen.