Lehman and Weibring both had a 5-under 67 at the Sunriver Resort Crosswater course to lead five players by a shot in the fourth major event on the Champions Tour.
Among those at 68 was Corey Pavin, who must decide by Sept. 7 which four players he will add to the U.S. Ryder Cup team he will captain in Wales later this year.
Pavin was joined in a tie for third by Fred Funk, Bob Gilder, 2008 champion Fulton Allem and two-time winner Gil Morgan.
Weibring, a five-time winner on the Champions Tour, had the lead for most of the round until Lehman tied him while playing in the day's final group.
Among those at 3-under 69 was Bernhard Langer, winner of both the U.S. Senior Open and British Senior Open this year. He captured those events in consecutive weeks.
Langer is trying to join Gary Player as a winner of three straight major events on the Champions Tour.