About starting "early" - be careful. I don't know what "early" is in your area but you can kill them with either nitrate poisoning or acidosis (or both, I guess).

The corn plant needs to be mature and as brown as possible. The nitrate migrates down the stalk as the plant matures and dies.

Steers will overdose on pure corn if you let them. Limit the area open to them at first and have hay and mineral available free choice along with a lot of good water.  You can gradually increase the area as they get used to the corn and it dries down. Electric cross wires help a lot.

Remember cattle will trample 40 acres of stalks etc until they find every last ear. Make them eat at least some husks and upper leaves. Do not make them eat the lower stalks where the nitrates and little nutrtion are.

I don't know anything about adding oats. "Getting the nitrogen out early" does make me more concerned about nitrate poisoning. I have been gradually cutting back on the N I apply to my grazing corn and don't put my steers on it until about 4 weeks after weaning. I would not put out excess N.

Good luck but start slow and carefully. It is not as easy as it may look.

Jim at Dawn