Preheat the oven to 375F.
Wash and finely chop the broccoli head, then set aside.
In a large baking dish, lay each chicken breast side by side in a single layer. Then sprinkle the garlic powder, salt and pepper evenly over the top of them to season.
Spread the broccoli florets evenly over the chicken, then pour the alfredo sauce over the broccoli and finally top with the mozzarella cheese.
Place in the oven on the middle rack for 40-50 minutes or until the chicken is cooked through and the broccoli is tender.
Remove from the oven and allow to cool for 5-10 minutes. Then serve hot over pasta, rice, mashed potatoes, or sautéed spinach.