Preheat the oven to 350 degrees F. and spray an 8x8 baking dish with cooking spray.
In a large bowl, mix the Greek yogurt, cheddar cheese, 2 tablespoons of Parmesan cheese, garlic powder, onion powder, salt, and pepper.
Once combined, stir in the steamed broccoli and cooked chicken breast.
Spread the mixture evenly into the baking dish. Sprinkle the remaining Parmesan cheese on top.
Bake for 20-25 minutes, until it is heated through and lightly browned on top. Let the casserole cool for 5 minutes before serving.