Sprinkle sliced zucchini with a little salt and set aside to drain for 30 minutes.
Preheat oven to 350. Spray a baking dish with cooking spray.
Combine all the other ingredients in a bowl and mix well. Add the zucchini. Put in the baking dish and bake for 35-40 minutes until golden and bubbly.
Notes
Nutrition: this recipe has 8 servings. The nutrition facts are for ⅛th of the zucchini gratin.To Reheat: warm the oven to 325 degrees and reheat the casserole for 10-15 minutes or until it is all the way hot. You can also warm it in the microwave on a microwave-safe plate for 1 minute or so. Substitutions: swap the feta for mozzarella or cheddar cheese. Additionally, parmesan cheese is a nice option as well.