Did you know... it's normal for dogs and cats to eat grass?
PetSmart Banfield, The Pet Hospital®
It's normal for dogs and cats to eat grass. In fact, dogs in the wild eat grass to supplement their diet with vegetation. You don't have to discourage your pet from nibbling on grass unless the ground has been treated with herbicides, insecticides or fertilizers, or unless eating grass causes vomiting.
Banfield, the Pet Hospital