Vicente Fernandez bogeyed the last two holes to fall out of a tie with Archer and take second place alone at 5-under 66. Rodger Davis has sole possession of third after posting a 4-under 67.
Archer wasted no time breaking into red figures with a short birdie putt at the first and recorded a pair of nice par saves at two and four. He drained a 10-foot birdie putt at the 610-yard, par-5 fifth and added a 15-footer for birdie at No. 6 to reach 3-under par.
He ran into trouble at seven when his 4-iron approach landed in a greenside bunker. Archer blasted out to four feet but missed the par save.
That bogey was the lone blemish on Archer's scorecard. He roped a 4-wood to 10 feet at the par-5 10th and sank the eagle putt. Archer holed a 12-foot birdie putt at 11 and made it two in a row with a 40-footer at the par-4 12th.
Archer saved another clutch par at 14 with a tricky four-footer and made a 10-foot birdie putt at No. 15. He nearly holed his tee ball at the par-3 closing hole, but missed the 12-footer which would have matched the 18-hole tournament record and allowed the 63-year-old to shoot his age.
'I hit the ball straight on the ones you had to hit it straight,' said Archer, whose 64 was his lowest round in 23 starts in 2002. 'The greens are beautiful here if you can read them. They don't have a real pattern to them.'
Archer has not won on tour since the 2000 MasterCard Championship and has not owned the first-round lead in a Senior Tour event since the 1999 Nationwide Championship.
Fernandez was on fire on the front nine at Oak Hills. He birdied three in a row, starting at the fourth, with all putts coming from inside 10 feet. He holed an eight-foot birdie putt at No. 8 and closed out his front nine with a 12-footer for birdie at the par-3 ninth.
Fernandez looked unstoppable after a four-foot eagle putt at the 10th, but he cooled. He collected six pars in a row from 11th, but flew the green at No. 17 with a wedge. Fernandez pitched to 15 feet and missed the putt to go to 6-under par.
He landed in a bunker at No. 18 and missed the six-footer for par. The 56-year-old still posted a 66 and is in the hunt after withdrawing from last week's Napa Valley Championship with a back injury.
'The results have not been good this year,' said Fernandez, a three-time winner on the elder circuit. 'I have had some injuries that have kept me from practicing as much as I could. Today's round was really unexpected.'
Stewart Ginn, Dana Quigley, Mike Hill, Bruce Summerhays and John Bland share fourth place at minus-3.
Tom Watson, Bruce Fleisher, Gil Morgan and 2002 Senior PGA Championship winner Fuzzy Zoeller are part of logjam in ninth at 2-under par.
Larry Nelson, the 2001 champion, opened his title defense with a 1-under 70 and is tied for 19th place.
Full-field scores from the SBC Championship