As of March 2015, two simple zucchini casserole recipes on AllRecipes.com are Zucchini Casserole and Zucchini Casserole II. Both of these recipes have preparation time of 15 minutes.
To make Zucchini Casserole, preheat the oven to 350 degrees Fahrenheit. Spray a 9-by-13-inch cooking pan with cooking spray. Place six sliced zucchini in a large saucepan, cover with water and boil for around two minutes. Drain the zucchini and set aside.
Whisk together two beaten eggs and 1 cup of mayonnaise. Stir in one small, diced onion, 1 cup of grated Romano cheese and 1/4 teaspoon of ground black pepper. Add the squash and pour the mixture in the baking pan. Sprinkle with 24 crushed, buttery crackers and dot with 2 tablespoons of diced butter. Bake for 30 to 40 minutes until firm in center.
To make Zucchini Casserole II, preheat the oven to 350 degrees Fahrenheit and grease a 2-quart casserole dish. Cook 6 cups of diced zucchini in lightly-salted water for around five minutes. Drain, place in a large bowl, and add one 10.75-ounce can of condensed cream of mushroom soup, 1 cup sour cream, 1/2 cup chopped onion and 1 cup shredded carrots.
Mix one 6-ounce package of dry bread stuffing mix and 1/2 cup melted butter. Layer the bottom of the casserole dish with the stuffing mixture, add a layer of the zucchini mixture, and top with another layer of the stuffing mixture. Bake for 20 minutes until top is golden brown.