Jiyai Shin and I.K. Kim carded 5-under 66s on Saturday to move into a share of the lead after three rounds of the Jamie Farr Owens Toledo Classic.
Shin and Kim were joined at 11-under-par 202 by So Yeon Ryu and Hee Kyung Seo. Ryu, who beat Seo in a playoff at the 2011 U.S. Women's Open, shot 67, while Seo posted a 3-under 68.
Second-round leader Chella Choi managed a 1-under 70. She stands alongside Inbee Park (69) and Mika Miyazato (69) in fifth place at minus-10.
Angela Stanford carded a 2-under 69 and headlines a group of four players tied for eighth at 8-under-par 205 at Highland Meadows Golf Club.
Shin, the only leader that had a bogey-free round, opened with a birdie on the first. After four straight pars, she birdied the sixth and eighth to move to minus-9.
The 8-time LPGA Tour winner cruised to five pars in a row from the ninth. Shin birdied the par-3 14th to get to 10-under. She grabbed a share of the lead with a birdie on No. 17.
"Today was another wet day, so I just tried to keep focused, try not to make a bogey. I made five birdies today," said Shin. "My shot making was better than yesterday. So I played much better today."
Kim, who missed a short putt that would have given her the Kraft Nabisco title earlier this year, birdied the first, but gave that shot back when she faltered to a bogey on the fourth. She erased that mistake with a birdie at the sixth.
The 24-year-old Korean made the turn at minus-8 thanks to a birdie on No. 9. Kim converted back-to-back birdie efforts at 12 and 13. Like Shin, Kim birdied the 17th to finish at 11-under.
Ryu tripped out of the gate with a bogey at the first. After four pars, she got that shot back with a birdie on the sixth. She ran off six consecutive pars from the seventh.
Last year's U.S. Women's Open champion caught fire down the stretch. After converting a birdie effort on the 13th, Ryu poured in three straight birdies from the 15th to jump to 11-under. She parred the last to end there.
"I think today I had really good patience out there. The front nine my putting wasn't great, but the back nine was really great, so I really happy with that," Ryu admitted. "The last few tournaments I've been struggling with my putting, but now it's really great. I hope tomorrow my putter works really great again."
Seo also faltered to a bogey at the first. She got that shot back with a birdie on the eighth and made it two in a row as she birdied No. 9.
Around the turn, Seo stumbled to bogeys at 11 and 12. The 2010 Kia Classic winner got those shots back when she holed out for eagle on the par-4 13th.
Seo grabbed a share of the lead with birdies on 15 and 17.
Hee-Won Han (70), Pernilla Lindberg (70) and Jacqui Concolino (69) stand alongside Stanford at minus-8.
NOTES: Na Yeon Choi, who is considered the defending champion as this event was last played in 2010, managed a 1-under 70 and finished 54 holes at 2-under 211...All four leaders have won an LPGA Tour event with Shin's eight titles being the most among the group.