Overnight leader Rob McMillan carded a 2-under 70 and is tied for second place with Rob Johnson and Rob Oppenheim, who both posted rounds of 4-under 68. The trio is knotted at 9-under-par 207.
Quiroz mixed two birdies and a bogey on his front nine, but after he missed a short birdie putt at the 10th, he changed his philosophy.
'I missed a short putt on the 10th for birdie, and after that I said to myself, 'Let's change, man. Be more aggressive,'' said Quiroz.
He tallied two birdies early on the second nine but dropped a shot at the 14th. Quiroz rebounded with a birdie at the next hole and that was enough to give him the outright lead.
Quiroz, who has represented Mexico in the WGC-World Cup, won the 2002 MTS Classic, but came back from five down in the final round. Now he will have to sleep on the lead on Saturday night.
'It feels great to be the leader, but we still have one more round to go,' said Quiroz. 'Tomorrow I will try to play the same as today, solid and calm. Stroke by stroke and not force things.'
Doug McGuigan (67) and Matt Weibring (70) share fifth place at minus-7. Stephen Woodard shot a 1-under 71 and is alone in seventh at 6-under-par 210.
Andy Matthews (73), Kris Mikkelsen (71), Paul Danielson (71) and Rob Labritz (71) are tied for eighth place at minus-5.