Annika Sorenstam, who is looking to complete the career grand slam, stands alone in third place at 4-under-par 68. Se Ri Pak leads a group of seven players tied at 3-under-par 69, including Jenny Rosales, Georgina Simpson, Karen Stupples, Shani Waugh, Lorie Kane and Christina Kuld.
Webb did not get off to a good start when her tee shot at the par-3 fifth found a greenside bunker. She left her second shot in the bunker, but managed to salvage bogey.
She came right back, however, to birdie the next to get back to even par. The Australian followed that up with another birdie at the seventh.
Around the turn, Webb struggled with a bogey at the 10th. She missed the green right and was unable to get up-and-down for par. Webb came back to two-putt for birdie on the par-5 11th.
Webb dropped a 6-iron within eight feet to set up birdie at the 14th. She came right back at the next when she rolled in a 25-footer for eagle to move to 4-under. She capped her round by running home a 40-foot birdie putt on No. 17 to grab a share of the lead.
'The weather conditions were a lot more favorable than we thought this morning, so the course probably played as easy as it can,' said Webb. 'Anything under par around here I think is a great score no matter what the conditions are.
'So I was really glad to keep the ball in play for the most part of the day, and I made a couple of really long putts out there.'
Webb, who finished fifth at the Evian Masters last week, is trying to use that momentum to her benefit this week.
'Right now I have quite a bit of momentum going,' said Webb, a three-time winner of this event. 'I feel comfortable on the golf course. One of the things I've struggled with is feeling comfortable on the golf course. Just standing out there confidently and hitting shots, I did that pretty much all day today.'
Ward got on the board when she dropped a wedge within four feet to set up birdie at the fourth. She followed that with an up-and-down birdie at the par-5 sixth. The Texan came right back to birdie the par-5 seventh to move to 3-under.
However, she could not maintain that momentum. Her drive found a fairway bunker at eight and she was forced to pitch out. Ward's third found a greenside bunker, but she managed to get up-and-down for bogey.
On the back side, Ward birdied the par-5 11th. She made it two straight by sinking a 20-footer for birdie on the 12th and capped her round by sticking a wedge 10 feet from the cup for birdie on No. 16.
'I hit a lot of good iron shots and always gave myself an opportunity,' said Ward. 'I think I only missed one or two greens, and whenever you have a birdie putt -- whether it's 15 feet or 20 feet -- out here, anything on the green is usually good.'
Sorenstam, who owns three wins this season, mixed six birdies and two bogeys over her round. She stumbled out of the gate with a bogey at the third but quickly recovered that stroke with a birdie at the next.
The Swede stuck a 9-iron within two feet at the ninth to begin a run of four birdies in a six-hole stretch. During that run, she also birdied 11, 12, and 15.
But, she dropped a stroke at the 16th after her drive found a fairway bunker. After a pitch out of the bunker, her third missed the green right. She atoned for that mistake when she drained a 32-footer for birdie at the 17th.
'The course is in such good shape, especially the greens,' said Sorenstam. 'They are very, very true. I think that's why you see a lot of low scores. Once you are on the green, if you hit a good putt, you know it's going to go in and obviously that's helpful.'
Patricia Meunier-Lebouc, who won the season's first major at the Kraft Nabisco Championship, leads a large group of players at 2-under-par 70. Helen Alfredsson, Gloria Park, Danielle Ammaccapane and Rachel Teske are also among 13 players at minus-2.