Gulbis, playing just her seventh event since joining the tour full-time, recorded seven birdies to a lone bogey to reach 11-under.
'I'm just excited, really excited, to be here, and it's nice to see my game finally getting better,' Gulbis said. 'I kind of got off to a little bit of a rough start. I hit the ball really well last week and have just progressively gotten better this week.'
Overnight leader Brandie Burton shot 2-under 70 to drop into a tie for second place with Pat Hurst (67) at 10-under 206.
Annika Sorenstam (70) held the lead at 11-under for two holes but slipped with two consecutive bogeys. She was two strokes back along with Grace Park (67). Laura Diaz (70) and Danielle Ammaccapane (70) followed at 8-under 208, and Se Ri Pak (66) topped a group four strokes back at 207.
Gulbis, the California Women's Amateur at age 14, was an All-American at the University of Arizona last season. She tied for third in the LPGA qualifying tournament last year, earning exempt status for this season.
Full-field scores from the Aeurs Electrolux Championship