Jones, who posted a 66 in Thursday's opening round, came back after Friday's rainout and shot one-under-par 71 for a seven-under 137 total he shared with compatriot James Nitties and Americans Brett Wetterich and Jimmy Walker.
First-round leader Matt Jones of Australia bogeyed his last hole Saturday to slip into a four-way tie for the lead at the halfway mark of the rain-hit Texas Open at the Oaks Course at TPC San Antonio.
Jones, who posted a 66 in Thursday's opening round, came back after Friday's rainout and shot one-under-par 71 for a seven-under 137 total he shared with compatriot James Nitties and Americans Brett Wetterich and Jimmy Walker.
The course was drenched by 3.15 inches (8cm) of rain on Friday when play was officially postponed for the day. Overnight rain made for a soaking of nearly five inches in the 24-hour period.
Nitties registered five birdies in a flawless round of 67 to match the score posted by Walker. Wetterich had a see-saw day of seven birdies and three bogeys for 68.
Twenty-eight players are within four shots of the lead. Players will go off split tees in groups of three Sunday in the hope of getting in all 36 remaining holes of the tournament.
"Thirty-six holes is going to be a long day on this golf course, mentally more so than physically," said 30-year-old Jones from Sydney.
"So if I can keep control of my mental side of things and play, let everything else happen, I should be all right."
Nitties said he thought his level of fitness could be an advantage over 36 holes.
"We've already done it twice this year in Puerto Rico and felt pretty good there," said Nitties, 27, from Melbourne. "I'm pretty fit so obviously that's going to help."
Seven players were tied on six under par, including Australian Aron Price, South African Garth Mulroy and US Ryder Cup player JB Holmes.
Moving into contention was world number seven Ernie Els of South Africa, the top-ranked player in the field, who shot 68 for five-under-par 139.
Zach Johnson, the 2007 US Masters champion who was trying to emulate Arnold Palmer by winning the event for a third year in a row, rebounded from a miserable opening round to shoot 68 but missed the cut due to his first-round 80.
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