The bogey-free trip around the course left Lee level with Mexico's Abraham Ancer, Canada's Mackenzie Hughes and Americans Ryan Armour, Bronson Burgoon and Zack Sucher.
Britain's Paul Casey arrived at the par-four 18th in a share of the lead but failed to hit the green with his approach and then settled for a closing bogey after missing a 16-foot par putt that left him in a group of six players one shot back.
Patrick Cantlay was also cruising along with a chance to grab the outright lead until a bad swing at his penultimate hole ultimately left him two strokes behind the leaders.
Cantlay, who won the Memorial Tournament less than three weeks ago, started on the back nine and was tied for the lead before a double-bogey at the par-three eighth where his tee shot found the water in front of the green.
The American, who has eight top-10 finishes in 15 events played this season, closed with a par for a four-under-par 66 that left him in a share of 13th place.
"Just hit it a little fat, and it's got to get up in the air to get the wind," Cantlay said of his tee shot at eight.
"It was downwind and didn't get the wind because I hit it fat and it went in the water."
Norwegian Viktor Hovland, who was the low amateur at last week's U.S. Open, shot a three-under-par 67 in his professional debut to sit tied for 25th.
Tournament favourite Brooks Koepka, fresh off a runner-up finish at the year's third major, mixed four bogeys with three birdies for a one-over-par 71 while defending champion Bubba Watson (69) was five shots behind the leaders.
Among the other notables in the field were Phil Mickelson (67), world number seven Justin Thomas (68), British Open champion Francesco Molinari (69) and three-times major winner Jordan Spieth (73).
(Reporting by Frank Pingue in Toronto; Editing by Greg Stutchbury)
