McCarroll, who caddied for John Henry as he won the Get Back to Golf Tour grand final at Dumbarnie Links on Sunday, set the pace in the Lawrie-owned circuit’s season-ending Carnoustie Tour Championship.
On a day when the scoring average was 74.86 on the Championship Course at the Angus venue, McCarroll carded a four-under-par 68 to lead by a shot from Ryan Campbell.
Derry man McCarroll started with a bogey-5 before picking up birdies at the third and ninth to be out in 35. It was a case of deja vu as he started for home with a dropped shot, but, in addition to the closing two holes, he also birdied the 11th and 14th on the inward journey.
Campbell, who landed his first professional win with a victory on the circuit at Blairgowrie last season, was two-over after three holes but stormed home in 32, having made birdies at the 11th, 12th, 14th, 15th and 18th, as well dropping a shot at the par-3 16th.
Four players - Scottish trio Ollie Roberts, Fraser McKenna, who started with three straight birdies, and Scott Young, who eagled the par-5 sixth, as well as Englishman Jordan Sundborg all opened with 70s.
In the testing conditions, Graeme Robertson, John Gallagher, Kieran Cantley and Eric McIntosh were the only others to break par, with Louise Duncan having to settle for a 78 on her return to the venue where she tied for tenth as an amateur in the 2021 AIG Women’s Open.
Order of Merit leader Jack McDonald opened with a 73, as did nearest challenger Danny Kay, with Cantley the other player in that season-long title hint, which will see the winner secure seven Challenge Tour starts next year.
Elsewhere, bad weather hit the opening round of the PGA EuroPro Tour’s Matchroom Tour Championship at Lough Erne in Enniskillen, where Michael Stewart was among the players still to complete their circuits following a suspension.
Stewart sits on three-under after 12 holes and sits alongside compatriot Chris Maclean, who got finished, as did Welshman James Frazer, who leads in the clubhouse on five-under.