Jeff Gove, Sonny Skinner, Mark Hensby and Scott Gump are tied for fourth place at 4-under-par 68.
Ogilvie collected two birdies on his front side but did most of his damage on the second nine. He birdied four of his first six holes on the back but dropped his only shot of the round at the par-3 16th. Ogilvie closed with a pair of pars to hold on to his spot atop the leaderboard.
'I holed a lot of four to seven-footers for par, but I missed a little one for my bogey,' said Ogilvie, who was a member of PGA Tour the last four seasons. 'It was a round that could have been even-par as well as 5-under.'
Carmichael opened on Clearwater's second nine and mixed three birdies and two bogeys for a 35. He tallied three birdies over his first five holes on his second nine and added a birdie at the par-3 ninth for a 67 of his own.
Freeman played later in the afternoon, when skies were cloudy and temperatures were down. He birdied three of his first five holes but tied for the lead with a pair of birdies at Clearwater's back-nine par-5s, the 10th and 14th.
Freeman bogeyed the par-4 15th to fall out of first, but a birdie at the 17th gave him a share of the first-round lead.
Andrew Buckle, Craig Spence, Adam Crawford, Ryan Palmer and David McKenzie share eighth place at minus-3.
Peter O'Malley, the 2002 Clearwater Classic champion, opened his title defense with an even-par 72.