Do you feed your dogs any fruits and vegetables? It may just be craving vegetation. I have heard that feeding them greenies a couple times a week can help curb the desire to eat grass. Sometimes dogs will eat grass if they have an upset stomach, but if the do it every day I would doubt that is what is causing it. Careful with the greenies tho, Zeus is only a puppy and he will chew on a regular size greenie for a couple minutes then swallow it whole.