[LoriF]

I would say feed them separately but next to each other with a barrier fence for a few days. That way he will get used to eating with the pony nearby. There is going to be a time when the horse is going to run the pony off until they become friends. Even when you feed in the same pasture, pen or wherever they are together, still feed them at a distance apart or separately if hard feed. Two equines would mean three or four piles of hay so they can move around and decide on their own who gets what pile.
All of this is normal horse behavior.

 

[Knave]

We usually keep horses over a fence for a week or so and then throw them together. We expect some normal herd dynamics. There will be some fighting and biting, and someone getting ran around. Definitely we feed in separate piles, and if too big a problem we add one extra.

Yet, unless someone is truly getting their butt handed to them, like cornered in a corral and just beaten and we figure there will be a broken leg, we let them work it out.

 

[LoriF]

At the place where I am boarding, they finally got their pastures fenced in. My two girls were the first in there. Then another horse came (a pretty arabian cross mare) My young mare didn't care and they were friends in a couple of days. My older mare chased the poor thing around running her off when she got too close. One week later and they are all relaxing together and I watched my older mare and the new one running together, bucking and playing.

They just have to work it out.