This simple zucchini casserole is an ideal way to use up abundant summer zucchini. It bakes up with a light quiche-like texture and works well as a side dish, a meatless main, or a crowd-pleasing potluck contribution.
Zucchini Casserole
This healthy zucchini casserole has been a favorite for many years. The recipe is straightforward and flexible: shredded zucchini, a binder of Bisquick (or a homemade substitute), eggs, a touch of cheese, and simple seasonings. The final texture is reminiscent of a crustless quiche—moist but firm enough to slice. It reheats nicely, freezes well in portions, and can be adapted to many flavor profiles by switching herbs, spices, or cheeses. It’s perfect for brunch spreads, light lunches, or served alongside grilled proteins for dinner.
How To Make Zucchini Casserole
This recipe is quick to assemble. Grate and drain the zucchini, combine the ingredients, transfer to a greased baking dish, and bake until set and golden. For best results, remove as much excess moisture as possible before mixing so the casserole doesn’t become watery.
- Preheat the oven to 350°F (175°C) and lightly oil a 9 x 13-inch baking dish.
- In a large bowl, combine 4 cups grated zucchini (well drained), 1 1/4 cups Bisquick (or substitute), 1/3 cup minced onion, 3 large egg whites (beaten), 1 large beaten egg, 1 tablespoon olive oil, 1/4 cup grated Parmesan, 1 teaspoon kosher salt, and 1 teaspoon chopped parsley.
- Pour the mixture into the prepared dish and bake until golden and set, about 45–50 minutes. A toothpick inserted in the center should come out clean.
Bisquick Substitute
If you don’t have Bisquick, you can mix a quick homemade baking mix that works well in this casserole.
- 1 1/4 cups all-purpose flour (or gluten-free flour blend)
- 1 1/2 teaspoons baking powder
- 1/2 teaspoon kosher salt
- 1 tablespoon oil or melted butter
Combine the dry ingredients, stir in the oil or butter until evenly distributed, and use this mixture as a 1:1 replacement for Bisquick. Double or triple the batch if you plan to bake more dishes.
Serving Suggestions
- For brunch, serve slices with fresh fruit and savory breakfast patties or sausages.
- For a light dinner, offer the casserole alongside grilled chicken, fish, or steak and a crisp green salad.
- To present it as an appetizer or potluck dish, cut into small squares and serve warm or at room temperature.
How to Reheat Zucchini Casserole
Store leftover casserole covered in the refrigerator for up to three days. Reheat individual portions in the microwave until warm, or reheat in a 350°F oven for 10–15 minutes until heated through. If reheating from frozen, thaw overnight in the fridge and warm in the oven for best texture.
Frequently Asked Questions
Do I need to peel the zucchini? No—zucchini skin is thin and adds color and nutrients. Grate it whole.
How do I drain grated zucchini? After grating, place the zucchini in a clean dish towel or several paper towels and squeeze firmly to remove moisture. You can also let the grated zucchini sit in a colander with a towel over it for an hour to drain. Removing excess liquid is important to avoid a soggy casserole.
Can I use a different pan size? A 9 x 13-inch pan is recommended for even baking. If you prefer thicker slices, bake in a 9 x 9-inch pan but be prepared to reduce oven temperature slightly and extend baking time to ensure the center cooks through.
How can I make this gluten-free? Substitute a gluten-free flour blend in the Bisquick substitute or use a gluten-free baking mix in place of Bisquick.
Variations and Flavor Ideas
- Yellow squash: Swap yellow squash for zucchini if that’s what you have on hand.
- Herbs and spices: Add Italian seasoning, a pinch of garlic powder, or onion powder for extra depth.
- Fresh herbs: Fresh basil, chives, or dill make excellent additions and brighten the flavor.
- Cheese variations: Try reduced-fat mozzarella, a sprinkle of cheddar, or a milder vegetarian Parmesan alternative if avoiding animal rennet.
Simple Recipe Card
Ingredients
- 4 cups grated zucchini, squeezed dry
- 1 1/4 cups Bisquick or homemade substitute
- 1/3 cup minced onion
- 3 large egg whites, beaten
- 1 large egg, beaten
- 1 tablespoon olive oil
- 1/4 cup grated Parmesan cheese
- 1 teaspoon kosher salt and fresh black pepper, to taste
- 1 teaspoon chopped parsley
Instructions
- Preheat oven to 350°F (175°C).
- Prepare a 9 x 13-inch baking dish with a light coating of oil or cooking spray.
- In a large bowl, stir together the drained zucchini, Bisquick (or substitute), onion, egg whites, egg, olive oil, Parmesan, salt, pepper, and parsley until evenly combined.
- Pour the mixture into the prepared baking dish and spread it evenly.
- Bake 45–50 minutes, until the top is golden and a toothpick inserted in the center comes out clean.
- Allow to cool slightly, then cut into 12 squares and serve warm.
Notes
If avoiding rennet in cheese, use a vegetarian or plant-based Parmesan alternative. The Bisquick substitute listed above (flour, baking powder, salt, oil) can be used in a 1:1 ratio for Bisquick.
Nutrition (per 1 square)
Approximate values: Calories 83, Carbs 11 g, Protein 4 g, Fat 3 g, Sodium 253 mg, Fiber 1 g, Sugar 2 g.
More Zucchini Ideas
- Zucchini Lasagna
- Tomato and Zucchini Frittata
- Crustless Summer Zucchini Pie
- Zucchini and Feta Fritters
- Zucchini Noodles (Zoodles)