England’s Davey Todd, a double Supersport winner at the North West 200 in May, was third fastest on the Milenco by Padgett’s Honda at 102.590mph, 0.268s behind Browne, with Magherafelt man Paul Jordan in fourth on the PreZ Racing Yamaha.
The opening Supersport race is scheduled to take place after practice on Friday.
Earlier, Browne clinched pole in the Moto3/125GP class on the Burrows Engineering/RK Racing Honda by 4.3s from Tobermore rider McLean, who is riding the ex-Robert Dunlop 125cc Honda.
Roads veteran Nigel Moore from Dungannon was third on his Moore Car Repairs Moto3 Honda ahead of Chris Meyer and Gary Jordan, both riding 125cc Honda machines.
Armoy is the final Irish road race meeting of the season after the calendar was decimated this year due to insurance issues.