I'll second what Tim said.
It's probably a better plan to feed hay in mulitple, smaller servings than to just put out a round bale and let the horse have at it.
As far feeds.....
Basicly, what Tim is talking about is a 14%-protein/6%-fat (pelleted) feed which has a realy good vitamin/mineral package blended-in. If you can't find 'Strategy', there are other brands which offer essentualy the same thing.
As far as oats go, I'm not a big believer in them.
To start with, oats are hard to digest because, "crimped" or not, it is still a seed. In fact, some of it don't digest at all and shows-up later as the little oat-grass shoots that grows in horse manure.
In the second place, it does produce a lot of energy but unless one is working an animal perty-hard, that particular aspect only serves to make them jittery and high-strung.
So in my opinion, everything considered, I just plain don't have much use for it.
Personaly, I'd rather spend $10 for a sack of good feed to start with.
At least that way, I'm perty satisfied that between the grass (or winter hay), the feed and maybe a mineral block to lick-on, mine are getting everything they need.
That's just my 2-cents worth.
Your Vet may say different.