Why does my dog eat grass?

They eat to settle an upset tummy

Some dogs will eat grass to force themselves to throw up. They may just need some food to settle their belly.

Dogs can't digest grass because they don't have the enzymes that are needed to break down the fibers. This means that there is very little nutritional value in the grass for the dogs. It's possible that the dog is just eating it to eat, especially if it's between meals. Another possibility is that it's due to feeling nauseous or having gastric reflux. Grass may be a temporary fix for both of those. Don't be surprised if your dog later vomits the grass though - this is normal. Some dogs may eat grass out of obsessive-compulsive behavior (I have personally seen dogs go after every single rock due to this.) If it's out of obsession, this behavior needs to stop. Another reason a dog may eat grass is that its not getting all of the nutrition it needs in its current diet.

Dogs eating grass is actually quite common and this form of pica does not usually cause too many problems. In fact, most veterinarians consider it a normal dog behavior.