Lee and Oh shot respectable two-under-par 69s in the first round, but find themselves five shots adrift of pacesetters Alena Sharp of Canada and South Korea's Youngin Chun at Highlands Meadows Golf Club.

Oh had three birdies to go with a lone bogey while World No.3 Lee mixed four birdies with two bogies.

Both are in a tie for 29th, three shots ahead of the only other Australian in the field, Robyn Choi.

The 38-year-old Sharp, winless on the LPGA Tour, had eight birdies and a bogey.

"I played really well right from the first tee shot," Sharp said. "I felt really calm this morning coming into this event. I always love playing here. I have great housing."

The 19-year-old Chun, also seeking her first LPGA Tour victory, had a bogey-free round.

"I didn't know I shot 64 today," Chun said. "The funniest thing I finish par on the 18 and then I saw the leaderboard and there is a seven-under and I was like, 'Who is that?' I asked my dad. 'I think I shot six, right?' He said, 'No, you're seven.' So it was me."

RIGHT: Chun shares the lead with Sharp after the first round of the Marathon Classic. PHOTO: Gregory Shamus/Getty Images.

American Stacy Lewis, who won the last of her 12 LPGA Tour titles in 2017, is a shot behind the leaders with German Caroline Masson, Swede Jenny Haglund and Spain's Azahara Munoxz.

"It was awesome," Lewis said. "The biggest thing is I hit 18 greens today. I've been working on the ball-striking a lot, so just really nice to see some results. Got a few putts to fall there on our last few holes."

The Texan had seven birdies and a bogey.

"It's a golf course I'm not necessarily 100 percent comfortable on," Lewis said. "I just had some really good golf shots today. Had some easy tap-in birdies. I haven't done that in a long time, in general."

Defending champion Jasmine Suwannapura opened with a 70.

Yealimi Noh, the 17-year-old from California who tied for sixth last week in Wisconsin in her LPGA Tour debut, had a 73.

Playing on a sponsor exemption after Monday qualifying last week, she had five birdies and seven bogies.