For my pasture board horses I provide free choice grass hay in large round bales. They get fed approx 3lbs Strategy 2X day with salt and daily dewormer. They are permitted to roam around the place as they please and due to their special circumstances we also groom and exercise them daily, but I charge more for that than I would the normal pasture boarder who would come out and visit their horses 2 or 3 times per week. They have available shelter for ugly weather and I can shut them in if I decide it's best (NOT normal for pasture board) and I will blanket and check to make sure they are dry and not losing weight in winter.
Most pasture situations I am used to provide your horse with either a private pasture or group pasture, depending on how much land and what kind of facilities they have, and normally there is at least a run in shed or trees for shelter in bad weather. Most pasture board in my area, the horses are out in a group, round bales provided and if the owner provides and feeds it, they can be grained but not normally. Normally they would not be blanketed nor taken into shelter and shut in in extreme weather. A salt block would probably be provided and free choice water and that's about it.
When I got the group of boarders I currently have, they had not been touched in 2 years, no one had checked their weight, dewormed them or done a blasted thing with them. No grooming, everyone had dredlocks (pasture dreds) and they were all at least 200 lbs underweight. If I were pasture boarding my horse I would be very serious about checking his weight weekly to make sure he didn't start dropping in winter or due to bullying. Most of the horses I have now were approx 3-4 when I got them, so if no touched for at least 2 years, you can imagine the rodeo we had here when trying to catch, groom, pick feet, etc. And the previous place charges more for pasture than I do for full board & care, go figure.