Ted Purdy posted a 69 to finish one shot back at 8-under-par 132. Billy Mayfair followed at 7-under-par 133.
Tiger Woods saw his streak of 142 consecutive cuts made come to an end as the top-ranked player in the world struggled to a 2-over 72 at Cottonwood Valley. He finished 36 holes at 1-over-par 141.
The longest current streak now belongs to Ernie Els, who shot a second-round, 2-over 72 to finish 36 holes at minus-4. This will be the 20th straight cut made for the three-time major winner.
Like Woods, O'Hair also played Cottonwood Valley in the second round and picked up his first birdie of the day at the par-4 third. O'Hair added a birdie at the par-4 seventh and hit his tee shot inside 30 feet at the par-3 ninth. O'Hair drained the putt to reach 7 under around the turn.
At the par-5 16th, O'Hair played his second shot to 3 feet and converted the short eagle try. The 22-year-old PGA Tour rookie parred his next two holes to complete a bogey-free round.
'I'm hitting the ball really well,' said O'Hair. 'I'm rolling the ball well on the greens and my lag-putting is good. It feels very good, I feel very comfortable out there and it's a nice situation that I'm in.'
Wetterich tallied his first birdie on the par-3 second at Cottonwood Valley. He added birdies at the fourth and the seventh to go out in 31, but stumbled to a bogey at the 10th.
The 31-year-old countered with a birdie at the 11th and parred his way in for a round of 67.
'I feel good,' said Wetterich. 'There's still two days, you know. I could fall back just as easily as I can keep going at the pace that I am. I'm just going to try to look beyond that.'
British Open champion Todd Hamilton carded a 67 to join Shigeki Maruyama, Steve Lowery and J.P. Hayes at 6-under-par 134.
Vijay Singh, who can regain the top spot in the world with a strong weekend, used a 67 to climb into a tie for ninth place at 5-under-par 135 with Phil Mickelson, Scott Verplank, Nick Price, John Rollins, Todd Fischer, Doug Barron, Heath Slocum and Omar Uresti.
Defending champion Sergio Garcia, who played the TPC at Four Seasons Resort on Friday, shot a 68 to finish in a group at 1-under-par 139.