England's Horsfield had fired a 61 en route to a top ten finish at last week's Betfred British Masters hosted by Lee Westwood, and added a 63 on day two at Forest of Arden Marriott Hotel & Country Club.
Seven birdies and an eagle took him to 13 under par and level with Spain's Garcia Rodriguez, who added a 69 to his opening 62.
Belgium's Thomas Detry is three shots back in third after consecutive rounds of 67, with Sweden's Alexander Björk and France's Antoine Rozner sharing fourth on nine under after both matched Detry's five under round.
Horsfield birdied the first and holed his approach for an eagle on the fourth before back-to-back gains on the sixth and seventh took him to the turn in 31.
Another birdie followed from eight feet on the tenth and there were further gains at the 12th, 15th and 17th in a flawless round.
“Holing a wedge from 110 yards on four was an obvious highlight,” he said. “I just got on a bit of a roll, birdied the par five 12th, then holed a nice 20 footer on 15 and ended up with a nine under round.
“I’m just having fun, it’s nice to be playing tournament golf again, it’s been a while for everyone and I’m just thankful of that, to get some tournaments going. I’ve been looking forward to it for a while and I’m just enjoying it.
“It’s different out here, not the same as what we’re used to but it’s just the world that we’re living in at the moment and you’ve just got to make the most of. We have a great opportunity to come out here and play tournament golf and I’m thankful that the European Tour and everyone involved have been able to make that happen.”
Garcia Rodriguez initially stretched his two shot overnight advantage with birdies at the third and seventh, only to then drop a shot at the ninth.
A birdie on the 12th was cancelled out by a bogey three holes later but the 31-year-old rookie finished strongly, birdieing the 17th and then holing from 20 feet at the last for a fifth gain of the day.
“Today the wind was tough, it was a lot windier and the pin positions were a little more complicated than yesterday,” he said. “But today I played very solid from the tee which was the key to only two bogeys and keeping solid.
“Yesterday was the putter, today it was difficult with the irons to get it pin high because it was so windy, but I’m so happy with my round today.”
Miguel Ángel Jiménez, on his record 707th European Tour appearance, added a 72 to his opening 64 to stay in the hunt for a fairytale ending to his special week by remianing eight under.