I had numerous friends in Texas that use to turn there horses out in large pastures in the winter and only check on them every couple of days. They would put out a large round bale of hay and the horses had ponds to drink out of and every few days they would check on them. I did have a few that would check once a day because they did not have access to round bales they would throw out enough hay for the day. The good thing about grass hay and even the oat hay is that it can easily be fed free choice with out any problems. Our use to eat a mix all the time. I would just make sure it is oat hay and not oat straw that you are feeding. If it is oat straw, I would rather leave out extra grass hay than the straw. The straw is more for bedding than feeding. Hope this helps, good luck.