In general, beer isn't the focus of the County, but it's slowly starting to find a toehold there.
There might not be a nicer area at an Ontario brewery than Parsons Brewing Company, which is just east of Picton along Highway 49. A quick bike ride, if you're so inclined, but also not the worst walk from central Picton either if need be (cabs in the County are, predictably, not the easiest to get). Beer isn't bad, and they're doing some experimentation in styles that is nice to see. Probably the best brewery in the County (though I haven't had Prince Eddy's yet).
555 Brewing is along Main Street -- good food, beer seemed decent after a day of cycling and drinking wine, but if you're buying anything to take away for later that evening at your AirBnB or hotel room, take a look at the canning date. I bought a couple cans of "Juicy" PA in May and later that night, after a few sips and realising there was absolutely no semblance of "juiciness" in it, checked the canning date, which was September, 9 months prior. My feelings on the place soured after that (rightly or wrongly).
Had a Midtown beer or two that were unremarkable, but fine.
Was surprised last time I was there that County Road Beer had shut down in order for Hinterland winery to focus on its sparking wines. That said, the Hinterland ciders that I tried while there were really very nice.
I basically always skip Barley Days, and while Lake on the Mountain (towards the ferry) has a great patio across the road, the beer is mediocre.
The County Canteen pub on Main St in Picton has the best taplist in the County, probably, with 20ish Ontario taps, including stuff from Bellwoods, Burdock, and Eastern Ontario breweries like Mackinnon and Town that aren't always so common in Toronto. I seem to recall that Hartleys Tavern just around the corner had a few beers to go with some really great food (the service we had one night was... strange... but the food was great), but we stuck with wine that night.
In Wellington, the Drake is pretty "big craft" and not at all exciting, but across Main St, The Courage was probably the best meal I've ever had in PEC and has a few decent beers.