Yes, you can freeze stuffed poblano peppers. Let them cool to room temperature then transfer to an airtight container or freezer-safe bag and freeze up to 2 months. Thaw frozen peppers in the fridge overnight then reheat in the oven at 350 F for 10-20 minutes until heated through. Note that freezing will change the texture of the poblano peppers. They'll still be safe to eat but they're best enjoyed right away or reheated after 1-2 days stored in the fridge.