Jon Mills posted a 67 to move into a tie for second place with Deane Pappas at 9-under-par 204.
Couch had a one-shot lead to start the day at The Glen Club and jumped out of the gate with birdies on each of his first two holes. He found trouble with a bogey at the third, however, but came back with a birdie at the par-5 fifth.
The 32-year-old hit his tee shot to 10 feet for a birdie at the par-3 11th, but he gave that shot back with a bogey at the par-4 14th after his second shot found a bunker.
Couch responded at the par-4 16th, despite hitting his drive into the rough. Couch played his second shot out to 14 feet and drained the birdie try to move to 11 under.
'I'm just going to try to play my game and do the best I can,' said Couch, who fired a 60 in the final round to win the Rheem Classic last month. 'You gotta stay patient.'
Mills ran off three birdies over his first five holes, but he stumbled to a bogey at the par-4 ninth to make the turn at 7 under. He recovered with a birdie at the par-4 15th and added a birdie at the last to finish within two of Couch.
'I feel like I have the game,' said Mills, who is trying to win for the first time on the Nationwide Tour. 'I figure if I just keep putting myself into position like I am that it will eventually come.'
Pappas played alongside Couch on Saturday and collected back-to-back birdies from the fifth to get to minus-9. At the par-4 eighth, Pappas dropped his second shot inside 5 feet and converted the birdie putt to tie Couch atop the leaderboard.
He cooled off on the inward half as the wind picked up and suffered a bogey at the 16th en route to a round of 69.
Jess Daley managed an even-par 71 to join Scott Gutschewski, Mario Tiziani, Paul Gow, Steve LeBrun, Kyle Thompson and Brendon de Jonge at 8-under-par 205. Ben Bates, Mathew Goggin, David McKenzie, Kevin Durkin and Scott Petersen were one shot further back at 7-under-par 206.