It depends. Some dogs can handle grass, and eating grass is harmless as long as the grass is not chemically treated. The speculation is that these dogs simply like the taste. Others vomit when they eat grass, and the vomiting could certainly settle their stomach. The speculation is that these dogs are eating the grass in order to settle their stomachs, but it could also be that they simply like the taste. I’d guess that if the dog eats grass only on occasion and throws up after eating the grass, then he is doing it to settle the stomach.