Paul Casey, Andrew McLardy and Andres Romero are knotted in second place at 6-under-par 67 at the PGA Centenary Course at The Gleneagles Hotel.
Two of last week's U.S. Open stars are part of a group tied for fifth place.
Kenneth Ferrie, who shared the 54-hole lead with Phil Mickelson, and Colin Montgomerie, who double-bogeyed the 72nd hole at Winged Foot when par would have won him his first major championship, both posted rounds of 5-under par 68.
Montgomerie, who played with Ferrie on Thursday, collected a pair of birdies at one and two, then drained a 10-foot birdie putt at the eighth.
At the 11th, Montgomerie sank a long birdie putt to reach 4 under. He added a short birdie putt at the par-5 12th, then got to 6 under par with a birdie at 17.
Montgomerie bogeyed the par-5 18th to fall into a tie for fifth, but was happy with the performance considering his final-hole collapse on Sunday.
'Every shot I hit, I thought about the last one I hit there and it is difficult to think about that,' acknowledged Montgomerie. 'The birdie at the first was very important and we can try and move forward.'
Ferrie was only 2 under through 11 holes, but a birdie at the 12th got him going. He closed with birdies at 16 and 18 to stay on the golf world's map one week after sharing sixth place.
'I am happy with my start considering I didn't know what to expect,' said Ferrie. 'I think I'm making a name for myself in a good way.'
The U.S. Open was last week, and so far Bjorn owns this week.
Bjorn began his opening round on the back nine and promptly knocked a 7-iron to 30 feet at the par-3 10th. He drained that birdie putt, then tapped in a short birdie putt at the par-5 12th. The Dane made it two in a row with a 3-footer at No. 13.
Bjorn parred No. 14 then went on another birdie run. He sank a 15-foot birdie putt at 15, two-putted for birdie at the par-5 16th and polished off three in a row with a 25-footer at the par-3 17th.
After parring 18 to make the turn at 6-under 31, Bjorn continued his fine play on his second nine. He hit a sand-wedge to 20 feet to set up birdie at the first.
At the par-5 second, Bjorn played a hybrid-club from the fairway to 4 feet. He converted the eagle putt to reach 9 under par through his first 11 holes.
'I probably mis-hit only one shot in those 11 holes and that was the third shot at 18,' admitted Bjorn. 'I search for perfection all the time and the first 11 holes were certainly nearly perfection. The first 11 holes were very special.'
Bjorn parred the third and found his only trouble of the round at the 211-yard, par-3 fourth. His 3-iron tee ball missed the green and his chip stopped 10 feet from the hole. Bjorn's par try stayed above ground, dropping him back to minus-8.
Bjorn parred his final five holes to grab the first-round lead, but couldn't help wonder what could have happened had he not struggled later in his round.
'At the end, it showed that I had only played one round on this golf course,' said Bjorn, who made the cut last week at the U.S. Open, but never threatened the top of the leaderboard. 'I wouldn't say I'm disappointed with the way I finished because I'm not, but at 9 under after 12 holes you feel you should walk off with something exceptional.'
Montgomerie and Ferrie were joined in fifth place by Stephen Browne, Miguel Angel Martin, Wade Ormsby and Francesco Valera.
Defending champion Emanuele Canonica is tied for 19th place after an opening-round, 3-under 70.