You might have heard about cats eating grass before, but maybe haven’t heard that dogs do the same. The good news is that this is totally normal  — while we cannot be 100% clear on the reason behind this, most vets would agree that it’s not unusual behavior.
It may be that your puppy is attempting to get more fiber in his diet, and/or that he is having some trouble digesting his food. Of course, we cannot know without seeing your dog, but you might try switching to an Australian Shepherd food with more fiber. Look for a recipe that uses either healthy, whole grains or one that contains fiber from vegetables and fruit.
Another possibility is that your puppy may have worms in his intestine. In this case, his grass consumption might frequently be followed by vomiting, and you may notice other symptoms such as runny stools or itching. If you suspect worms may be the cause of this behavior, please take him to the vet to get some professional advice.
Lastly, your puppy may just like the taste of fresh grass. As long as it’s not covered in harmful chemicals or close to any poisonous plants, this is not a cause for too much concern.