Suzann Pettersen, Sun Young Yoo and So Yeon Ryu all fired a 6-under-par 66 on Thursday to share the lead after one round of the season-ending Group Titleholders.
Last week's Lorena Ochoa Invitational winner Cristie Kerr, world No. 4 Na Yeon Choi, Lindsey Wright and Karine Icher are all one stroke behind in fourth place.
"Actually I had my coach here earlier in the week and he told me to grip down a little bit when I putt so I can hit more relaxed, so I think that kind of helped me a lot," said Yoo, who tallied nine birdies, a bogey and a double- bogey. "I rolled the ball pretty good, so I feel good with everything."
The top-3 finishers in each official LPGA Tour event qualified for the event, which includes the top-31 players on the money list and the top-13 players in the world rankings.
World No. 7 Jiyai Shin shot 68 at the Eagle Course at TwinEagles Club to share eighth place with Brittany Lincicome, Julieta Granada and Lizette Salas, while Karrie Webb, Danielle Kang, Anna Nordqvist and Cindy LaCrosse share 12th at minus-3.
World No. 2 Stacy Lewis, the only player to win four titles this season, carded a 70. She has already secured the 2012 Rolex Player of the Year award -- becoming the first American to receive the honor since Beth Daniel in 1994 -- but needs to win the $500,000 first-place check this week to have any chance of passing money list-leader and world No. 3 Inbee Park.
Park, who has secured more than $2.2 million in earnings, also shot 70 on Thursday.
Defending champion Hee Young Park and world No. 1 Yani Tseng both struggled on Thursday, carding a 76 and 75, respectively.
Michelle Wie is alone in last place at 9-over.
Pettersen fired six birdies on Thursday and was the only one of the three leaders to play bogey-free golf.
"I'm in it to win it," said Pettersen. "That says it all."
NOTES: Ryu is this year's Louise Suggs Rolex Rookie of the Year ... Last year, Hee Young Park collected her first LPGA Tour victory at the season-ending event. Park fired rounds of 71-69-69-70 to win by two strokes over Paula Creamer and Sandra Gal