People often ask me why dogs eat grass. Some dogs even dig the grass up and eat the roots and dirt as well. I believe that dogs were meant to have a varied diet, and that it is not really natural for them to eat just one type of food every day of their lives. And all animals generally enjoy fresh food. Having said this, dogs that consistently graze might be looking for extra minerals or other nutrients, such as fresh antioxidants that are found in grass and other raw vegetable material.
Sometimes our pets are cleverer than we realise. For example, some years ago I went hiking up a hill with a bunch of friends. Of course our dogs went with us. The breeds included Malinois, Jack Russells, a German Shorthaired Pointer and Border Collies. The dogs ran free whilst we puffed and panted our way up the mountain. About half way up we had a sit-down to recover our breath and enjoy the view. After a few moments, I noticed the dogs were disappearing around the side of an outcrop of rocks. Curious, I followed them. There within the protection of these rocks, was abundant if somewhat tatty-looking grass, which all the dogs were busy devouring. I found this most odd, as there was much more luxuriant looking grass growing nearby, which they all ignored. Surely such a motley crew of dogs from such diverse backgrounds couldn’t all need nutrients on the same kind on the same day. I pulled up some of the grass and put it in my pocket.
The next day at work, I presented this grass to the biology department at the University I was working for at the time, and asked why all these dogs wanted to eat it. The next day I got my answer. The grass was indigenous and contained small hair-like protrusions along its outer edge. The academics believed that on passing through the gut of the animal the coarse edges of the grass helped scour it out, thereby assisting in ridding the dog of internal parasites.
Whatever the reason for your dogs grazing habits, it is certainly not unusual for them to want to eat grasses, roots, etc.