Beverly Harvey Clarke has a facility just outside Collingwood, might be a Wasaga Beach number. She does outdoor board, has a nice but smaller arena. It is not a large facility, but she has great clients and it seems to be a fairly drama free spot. She has students showing at schooling shows, trillium and A.
Alpine is a large facility, so not sure if it would be what you are looking for and I don’t recall seeing horses outside all the time, so may not do outdoor board.
Candice Rainey at Signature Equestrian may do outdoor boarding. I know that she keeps a number of her own horses outside. There is no in house coach, but there is a lovely large coverall arena. Those in the area would know it as the old Greystone location.