The Austrian, eighth on The Challenge Tour rankings after victory in his native Austria at the start of the month, shot six birdies with a solitary dropped shot.
"It was a perfect start, because the conditions were quite tough," said the 31 year old former European Tour Qualifying School winner.
"It was almost as windy as it had been in the Pro-Am on Wednesday, so I was very pleased to shoot a 66. The greens here are always quite tricky, and with the wind also blowing it made for quite a tough day. So I couldn't have gone much lower than that."
Wiegele's bogey came when he three-putted the second, but he responded well with the putter and believes the confidence of his win in at the Karnten Golf Open by Markus Brier Foundation can be maintained.
"I had been struggling for a while with my putting, but I turned it around on the first day in Austria," he added.
"I struggled again on the second day with my putting, but the weekend was much better and then today was better again still. I actually putted pretty poorly in the Pro-Am, but I adjusted to the pace of the greens much better today."
His victory two weeks ago came thanks largely to a hole in one at the eighth - exactly the same hole he had aced 12 months earlier in the same event.
"It was unbelievable, especially with another hole in one on the eighth hole. I hit an eight iron like I did last year, and the pin was in the same position - but I didn't expect to have the same result!
"Last time I took the money but this time I think I'll keep the car, because it seems I'm destined to drive a Mazda! It was a great end to a great week, which started with me shooting a round of 62 - my lowest ever."
Ireland's Moriarty, a 31 year old Challenge Tour regular, also shot six birdies before a dropped shot at the last cost him the outright lead.
"I played very nicely," he said. "It wasn't as breezy as it has been over the past few days, so that helped. But I drove the ball really well, and set up a lot of chances - particularly early on. I got off to a great start with a birdie at the first, where I hit it pretty close.
"I did the same on the sixth, then I birdied ten, 12 and 13 to get to six under par. So at that point I was hitting a lot of shots close and also putting very nicely, but unfortunately I bogeyed the 17th after pushing my tee shot out to the right of the green, and I didn't manage to get up and down. But any time you shoot a 66 round here, you've got to be fairly happy."
French duo Michael Lorenzo-Vera and Charles-Edouard Russo form part of a five-way tie for third on three under, along with England's Andrew Marshall, Australian Wade Ormsby and Sweden's Joakim Backstrom.