Yes and mashed grains are even better. Extracting the sugars leaves a high protein feed. Golden Valley's owner has a beef ranch and the spent grains are an important part of the diet.
I suspect to the average-sized horse, the steeped grains from a 5 gallon batch would fall into the treat category.
One of my friends lives near a farm that has but one horse.
You can go out and not see any evidence of a horse but, in near perfect timing, as soon as the mash is done that horse comes around every time. He feeds it the spent grains. And the horse loves him for that.