Dick Mast, John Bland, Bruce Fleisher, Dana Quigley and Bob Gilder share second place at 6-under.
The elder circuit's newest faces had two different rounds on Saturday. Fuzzy Zoeller shot a 1-under 71 while Tom Purtzer, who held the lead through 13 holes when play was halted on Friday, is two off the lead at 5-under-par.
'I had lost my confidence on the PGA Tour,' said Purtzer, who turned 50 in December. 'The last few years I really struggled around the greens. Not having to make a cut really has helped.'
Heavy storms on Friday left Crandon Park Golf Club unplayable and the first round was scrapped. The tournament was reduced to 36 holes as a result.
Overton flew out of the gate on Saturday with an up-and-down birdie at the par-5 1st hole. He added a six-foot birdie at No. 4 and made it two in a row when he ran home a 15-footer.
He birdied the 7th to go out at 4-under 31 but caught fire once again at the start of his second nine.
Overton drilled a 15-foot fringe-putt birdie at No. 11 and made a beautiful par save from a bunker at the next hole. He played an 8-iron to four feet to set up birdie at the 410-yard 13th but squandered an opportunity at the par-5 14th when he reached the green in two, but three-putted for par.
The Monday qualifier capped off his round with a bunker-saving birdie at the par-5 last hole.
Overton was thankful that Friday's round was washed away because he was in the first group of the day and was 3-over par in the 18th fairway.
'Yesterday wasn't comfortable,' said Overton. 'We caught a break.'
Overton is playing in only his eighth event on the Senior Tour and after failing to crack the top-50 on the money list, he will need to either qualify on Monday for all of his events or receive sponsor's exemptions.
One other alternative would be to win this event and a one-year exemption on tour.
'I have to be able to play well in order to ask for sponsor's exemptions,' said Overton, who can be the first Monday qualifier to go on and win am Senior Tour event since Jim Ahern at the 1999 Canada Senior Open. 'Today was like a reprieve from yesterday. It was a marvelous turnaround.'
Fleisher used four consecutive birdies at the start of his second nine, all from inside 15 feet, to climb up the leaderboard.
'I was patient and knew I was hitting the ball good,' said Fleisher. 'You get away with a lot more when you're scoring easy.'
Purtzer is joined in a tie for seventh with George Archer, John Jacobs, Tom Kite, Walter Hall and Sammy Rachels at 5-under.
Full-Field scores from the Royal Caribbean Classic