No, oatmeal and oat fiber are not the same thing. Grinding the husk or hull of the oat grain makes oat fiber. Oatmeal is derived from the de-hulled oat groat. Is oat fiber a whole grain? No, oat fiber is not a whole grain, but rather the outer hull or husk of the oat grain. The grain is processed to separate the hull and the oat groat.