What to feed a horse really depends on a number of things.
Some horses don't need any feed, and are fine just being on pasture 24/7, or that plus some hay.
What is it you want to do with your horses? What kind of horses?
My horses personally eat Whole Oats, Rice Bran and Beet Pulp everyday twice a day- I have found that this is good for them for the work load and pasture schedule I have them on. They are stalled 12 hours, on grass 12 hours (right now with a round bale because it is winter), and get hay at night.