dog upset stomach

Question
I have an American Buuldog puppy who's 6 months old and weighs 73lbs. He vomitted up his food this morning and then vomitted up some mucousy yellow bile. His stool is normal. He won't touch his food and he keeps trying to eat grass so I know his stomach is sour. Should I let him eat grass or is there something OTC that I could give him that would help and be better for him?

Answer
How many times has he vomited?  If it is just the once then I would give him nothing for 12 hours and then offer him small amounts of palatable and easily digestible food such as cooked chicken and rice and feed him on small amounts of this for two days.  
If he continues to vomit over the next 24 hours or develops any other symptoms I would contact a vet.  Hopefully though he has just picked up something he shouldnt have out on a walk and it will clear up by itself.  If he wants to eat grass it will not do him any harm, it does not have quite the same effect on a dog as it does on a cat and many dogs eat it all the time whether they are sick or not.  My two eat so much sometimes I think they have confused themselves with the sheep! They are never sick from it though.
Hope this helps
Sarah