Brad Ott fired a 6-under 65 to move into a tie for second place. He stands alongside first-round leader Charles Warren and Brian Wilson, who shared the overnight lead with Tambellini, at 10-under-par 203.
Tambellini got off to a hot start at Hillcrest Country Club. He drained a 40-footer for birdie on the first. He then made consecutive up-and-down birdies on the second and third to open with three straight birdies.
Another sand save on the fourth set off a run of three consecutive pars. He dropped an 8-iron within two feet of the cup at the seventh for his fourth birdie of the day. He closed out his front nine with a 14-foot birdie putt on the ninth.
He moved to 15 under when he sank a 15-foot birdie try on the 13th. However, he stumbled to a bogey at the next. The 28-year-old then two-putted for birdie on the par-5 16th.
Tambellini found water off the tee at the par-3 17th. He nearly holed his third shot for par as it stopped one foot from the cup, but he settled for bogey.
'I'll try to steady it up Sunday and see what happens,' said Tambellini, who is searching for his first win on the Nationwide Tour. 'I felt like I was in control all day, except for the shot on 17. I just want to keep doing what I've done the par three or four months.'
Wilson opened with back-to-back birdies from the second, but was unable to make any further move. He dropped a stroke when he bogeyed the par-4 12th.
'I don't think I can hit it that bad again,' said Wilson. 'I hit the ball terrible on the back nine but I also got a lot of good breaks too. I just want to take it one shot at a time on Sunday.'
Warren reeled off four birdies on the front nine to get to 10 under. He continued to make his move with birdies on 11 and 16. However, he stumbled home, as he bogeyed the final two holes to drop back to minus-10 for the event.
'There is nothing you can do about it,' Warren said. 'You're going to make bogeys on holes out here you think you should birdie. But overall, a 67 on Saturday at this golf course is a good score.'
Fran Quinn carded a 2-under 69 Saturday. He shares fifth place at 8-under-par 205 with Jason Schultz and Tjaart van der Walt. Scott Gutschewski, Franklin Langham, Danny Briggs and Brett Wetterich are tied one stroke further back at minus-7.