If you have a high quality forage that will allow him to meet his growth potential, by all means turn him out.
If not, feed him around 3% of his bodyweight daily so that he has the diet to develop muscle, bone and organs the way he should. I believe it is better for him to have a little extra fat than it is for him to be stunted and deprived.
All these folks that tell you not to feed a bull grain have probably never developed one.
Feeding grain doesn't necessarily make one melt when he starts to work.
They never forget how to, or lose the instinct to graze.
I like my bulls to have at least a 3 lb. WDA minimum at yearling. This way I am somewhat assured he has not been deprived of nutrients during development and has plenty of growth potential in his genetics.
Furthurmore, if he gains well on grain, more than likely he will do the same on grass.