U.S. Solheim Cuppers Juli Inkster and Wendy Ward each fired rounds of 4-under-par 68. They share fifth place with Lorie Kane, Smriti Mehra and Gloria Park.
'I've been playing good for the last two months now,' said Gustafson, who won three times on the Ladies European Tour this season. 'I've had three wins in the last two months, so it's been working well.'
Gustafson is using her Solheim Cup experience to help her this week.
'Bringing your game from the Solheim Cup over here is tough because your mind set is very different, but it seems like I've been able to hold on to some of it,' Gustafson said. 'I think my confidence has gone up, and I've improved my chipping, so that helps.'
Gustafson, who won three of her five matches for the European Solheim Cup team, opened on the back nine at Lincoln Hills Club. She two-putted from short of the green for birdie at the par-5 11th and came right back with a 12-foot birdie putt at the next.
She pitched her third shot within three feet of the cup at 15 for birdie. The Swede dropped a sand wedge within three feet of the hole at 17 for her fourth birdie on her opening nine.
Around the turn, Gustafson rolled in a 20-footer for birdie at the first before two-putting for birdie at the next to climb to minus-6. She three-putted her way to a double bogey at the fifth.
The 39-year-old rebounded with a two-putt birdie at the eighth. She closed out her round by dropping an 8-iron seven feet from the cup for birdie at the ninth.
Park survived a pair of bogeys to grab a share of second place. She opened on the back nine with an eagle at the 11th and came back to birdie the next. She then stumbled to a three-putt bogey at the 13th and faltered to another three-putted bogey at No. 15.
She moved back to minus-2 with a two-putt birdie on the second. Park birdied the fifth and seventh before closing with another two-putt birdie at the eighth for a share of second place.
'I hit a lot of fairways and greens, but my putting gave me problems early in the round,' said Park. 'I just couldn't get the speed down for some reason. It's usually one of the strongest parts of my game.'
Ellis drained a pair of birdies on the back side. She dropped a shot at the third but birdied four of the next five holes to join the tie for second place.
Webb carded three front-nine birdies and moved to 5 under with an eagle on the 11th. However she bogeyed the 13th, but came back with a birdie on No. 15.
'The greens are a little inconsistent and a little bumpy,' said Webb. 'As you can see from my stats, I didn't have many long putts, but it's tough putting and is tough to read them, especially around the hole where they're a little bumpy.'
Beth Daniel and Suzann Pettersen, both Solheim Cup performers, lead a group at 3-under-par 69. They are joined there by Patricia Baxter-Johnson, Tracy Hanson, Angela Jerman, Emilee Klein, Yu Ping Lin and Miriam Nagl.
Defending champion Cristie Kerr finished in a tie for 39th at even-par 72.