Bob Gilder, David Edwards and Gary Hallberg tied for third place at 68 and six players were another shot back.
The Champions Tour event is being played at the TPC at Snoqualmie Ridge.
"I played real consistent. I hit the ball pretty straight today," said Simpson, who won the 1987 U.S. Open. "I had a lot of birdie putts. It was a really good round."
Wiebe birdied the 15th hole to take the lead but bogeyed 18 to fall into a tie with Simpson.
"The course was there for the taking and I played well most of the day," Wiebe said. "I like the way I am playing right now, I just made a couple of mistakes today."