Morgan won this event in 1997, when it was held at Kemper Lakes in Long Grove, Ill., and tied for third here last year with Tom Purtzer. His round Friday was one stroke off the course record set two years ago by Larry Nelson and Walter Morgan.
"This is more of a ball-hitter's course," Morgan said. "You have to be able to maneuver the ball here. I've played well here the last two years."
Purtzer had a hole-in-one and was tied with James Mason at 5-under 67.
Morgan began his round by hitting a 7-wood onto the green and holing a 50-foot eagle putt.
"I've been off for a couple weeks," Morgan said. "I got out here on Tuesday. I got off to a great start with the eagle on the first hole."
The warm conditions cooled a bit, but Morgan's play remained red-hot. He picked up another stroke with a tap-in birdie at the par-5 ninth, then birdied four of the last six holes.
"The weather was a little on my mind when I started," said Morgan, who had an early tee time. "I told myself if I got off to a good start and there was some weather, I'd be in good shape."
Morgan, 58, has won at least once in his last seven years on the Champions Tour. He has 21 career victories, but last year marked his first full season that he did not win more than one tournament.
Purtzer was just 2-under with four holes to play, but two-putted for birdie at 15 and then drained an eagle of his own at 16 -- a hole-in-one with a 6-iron from 198 yards.
Hale Irwin, the 2002 Champions Tour Player of the Year, shot a 1-over 73. He is winless in four events this season, although he has consecutive runner-up finishes.
One of those came in last week's MasterCard Classic, won by David Eger, who also had a 73.
Defending champion Tom Kite stumbled to a 74.