"I felt some pressure leading up to the first hole," said Lee, who is tied with Grant Strobel of Carlton Oaks Country Club behind Timothy Parun of Sail Ho Golf Club (69). "It's one of the best courses around and I got off to a good start.
"Basically, I knew where not to hit the ball and it was all about putting. I hit a lot of greens in regulation and I knew the course was going to play tough. My pars were good."
Lee registered 13 pars, three birdies and two bogeys on the 7,015-yard course that underwent renovations in 2009.
Lee finished one-under through nine holes. He notched birdies on the third, eighth and 17th holes.
Unlike Lee, Oakmont head Professional John Milligan encountered some difficulties after beginning the tournament with a disappointing 78.
Making his third appearance in the event, Milligan got off to a rocky start by bogeying the first and second holes before parring the third and fourth. However, Milligan then double-bogeyed the fifth, forcing him to catch up the remainder of his round.
"My short game was basically non-existent," said Milligan, who birdied the seventh hole and is tied for 62nd place. "I three-putted on one and two and got the bogeys and then got that double-bogey.
"On the fifth hole, I hit it over the green. I tried to ram putt it in. I had some wonderful opportunities on the back nine, but I just didn't hit some shots. My long game was average after the fourth or fifth hole."
Milligan finished with 11 pars, one birdie, four bogeys and a pair of double-bogeys.
Parun attacked the course by recording two birdies on his first two holes. In all, he recorded five birdies, 10 pars and three bogeys.
Strobel had five birdies, nine pars and four bogeys.
There is a four-way tie for fourth at 71.
Kevin Erdman of Altadena Golf Course, the husband of former Crescenta Valley High girls' golfer Courtney Renfro, finished with a 79 to move into a tie for 73rd. Rick Sessinghaus of Chevy Chase Country Club carded an 80 and is tied for 84th.
The field in its entirety returns today, hoping to make the cut that will determine Wednesday's final round. The top 11 finishers from the 54-hole stroke play competition will qualify for the 2011 PGA Professional National Championship, which will be held June 26-29 at Hershey Country Club in Hershey, Pa.
The champion from the section tournament will also receive one exemption into the 2011 Bob Hope Classic. The top two finishers will earn exemptions into the 2010 Soboba Classic Nationwide Tour event. The top 30 placements will receive exemptions into the 2010 California State Open, which will be held in November in Beaumont.