Have you ever seen your dog or any dog eat grass while they are outside? I was always told that if a dog ate grass, it was because their stomach was upset. I have researched why dogs do this because my puppy sometimes does it and I wanted to make sure she wasn't going to get hurt form doing it.
So the top 3 reasons why your dog eats grass when outside...
1. Boredom; if your dog doesn't get enough exercise he/she will eventually become bored and find other things to do to pass the time.
2. Nutritional Issues; Since dogs eat both meat and plant based food, they might search for that fiber to fulfill that need for that nutrition.
3. Upset Stomach; although there isn't much scientific evidence that this is true, some believe it to be true. most of the time vomiting follows the grass eating to remove the contents of the stomach, therefore helping the upset stomach.
After researching and reading all of that, I'm pretty sure my pup does it because of boredom, because she mostly jumps around and try to rip it and then shell just eat it. LOL she's funny. She is a nibbler so when she is laying in the grass being lazy, I find she starts to mess with and eat the grass! LOL