Question about bran...?

My horse is currently taking medicine that she doesn't like to eat, so I've been mixing it with a small amount of wheat bran and adding it to her feed (she eats it right up!). However, the barn ran out of wheat bran and won't get more for a week or so. The only bran-type things at the grocery store were oat bran and and Irish Oatmeal rolled oats. So will these work for right now? I only use about 2/3 cup with each feeding.