Hi! Laura Moore here. Over the years I have experienced this issue and had many questions regarding dogs(and cats) eating grass. The information thru my studies has been that it is not that they have an upset stomach and are trying to make themselves throw up.  It has also not been my experience that it is a deficiency in the diet. If your dog vomits after eating grass it is more than likely due to the sharp edges of the grass irritating the throat and causing the regurgitation of the irritant. I am aware of dogs, including my own, that have very good and balanced diets who love to eat grass especially in the Spring when it’s nice and fresh.  If you are interested in further conversations regarding this issue, you may want to read the full blog article by Dr. Jean Dodds regarding “Why Do Dogs Eat Grass?”  Just click on the link below. Hope this is helpful.