Eduardo Romero, Mikko Ilonen and Marcus Fraser each shot 68s.
Frost delayed the start by about 2 hours, and 44 players did not complete their rounds. They are scheduled to resume Friday morning.
Dredge, a Welshman who won the European Masters by eight strokes last year, eagled the par-4 sixth hole, where his 120-yard wedge shot spun back into the hole.
'It seems to suit me here,' Dredge said. 'I managed to hole a lot of putts in the 10-to-12-foot range when I had to. I went through a round where I didn't waste a shot today. It's not often you can say that.'
Of the five members of this year's European Ryder Cup team in the tournament, Robert Karlsson had the best start with a 69. Paul Casey and Lee Westwood shot 71s, while Darren Clarke and David Howell had 75s.
Tadd Fujikawa, the 16-year-old from Hawaii, did not finish his round. He was 5 over through 15 holes with three birdies and eight bogeys.