They each made six birdies and a solitary bogey, and moved to 9-under 135 totals, one better than overnight leader Lee Westwood.
Westwood carded a 70, dropping a shot on the final hole after hitting his second shot into the water.
Fellow Englishman Tyrrell Hatton (66), Austria's Bernd Wiesberger (67), South African Charl Schwartzel (67) and Dutchman Joost Luiten (69) were tied for fourth at 7 under in the season-ending championship of the European Tour.
Garcia looked in superb touch and, except for a couple of mistakes on the par-4 12th and par-3 13th holes, the latter resulting in his only bogey, seemed in control of the round.
"I try to enjoy myself as much as possible. Obviously, when you're playing well, it's a little easier. It was a good day," said the Spanish Ryder Cup star.
Molinari made his only bogey on the 10th.
"Maybe yesterday the start was even better, but (I) played solid pretty much all the round," the Italian said. "I had a little lapse in concentration on the 10th and then recovered well."
Race to Dubai leader Henrik Stenson stayed in touch with his rivals for the Europe No. 1 crown. The Swede shot a battling 3-under 69, to move to 3 under at the halfway stage, the same as No. 2 Danny Willett (70), and one behind compatriot Alex Noren (69).
Stenson was saved by a hot putter on a day when he wasn't his usual accurate self with his irons. An errant tee shot on the 13th hole injured a female spectator.
"I'm definitely not playing great, but I had some more chances and the putter was behaving a lot better than yesterday,' Stenson said. "It's a bit of a grind, but I'm hanging in there and fighting hard. I know the guys are going to come at me."
Meanwhile, defending champion Rory McIlroy improved on his horror start of 75 with a 68.
"Mentally, yesterday, I was still on holiday," he said. "I felt a bit better out there today."