Baked Zucchini Casserole with Crispy Parmesan Topping

If you enjoy zucchini, you’ll love this easy and flavorful zucchini casserole. It’s simple to prepare, nutritious, and makes an excellent side dish any time of year—great for weeknight dinners, family gatherings, or holiday meals.

This casserole is a delicious way to add more vegetables to your meals. Thinly sliced zucchini are briefly roasted to soften them, then topped with a creamy garlic‑parmesan sauce made from milk (or a non‑dairy alternative), garlic, cheese, and simple seasonings. The sauce is poured over the zucchini in the baking dish, finished with shredded cheese and seasoned breadcrumbs, and baked until golden and bubbly. Serve this zucchini casserole as a side with nearly any main course. It also adapts easily to vegetarian or vegan diets by swapping dairy cheeses for vegan alternatives.

Why you will love this zucchini side dish recipe

• Versatile: You can mix in other vegetables such as mushrooms or bell peppers, or season it to your taste.
• Healthy: The casserole highlights zucchini, a low‑carb, nutrient‑dense vegetable, making this a lighter, vegetable-forward side.
• Easy to make: Most of the work happens in the oven. Prepare the sauce, arrange the zucchini, assemble, and bake.

Ingredients, tips, and substitutes

• Zucchini – Green zucchini works well; yellow zucchini or a mix of both are great too.
• Salt and pepper to taste.
• Oil – Any neutral oil is fine; olive oil adds nice flavor.
• Onion – White, sweet, or red onion all work; finely grated or diced.
• Garlic cloves – Fresh garlic is preferred. If needed, substitute 1 tablespoon garlic powder.
• Milk – Use any milk you prefer; almond milk or 2% milk are both suitable.
• Cornstarch – Thickens the sauce. You can use a small amount of flour, but the texture may be slightly thinner.
• Oregano – Italian seasoning or dried basil are good alternatives.
• Cheddar cheese – Use regular or reduced‑fat cheddar.
• Parmesan cheese – Freshly grated or store‑bought both work.
• Bread crumbs – Seasoned or plain; use gluten‑free crumbs if required.

How to make this zucchini casserole from scratch

Preheat the oven to 425°F (218°C).

Place the sliced zucchini in an oven‑safe baking dish and season with salt and pepper.

Drizzle with 2 tablespoons of oil and toss gently to coat the zucchini evenly.

Bake for 10–12 minutes, or until the zucchini begins to soften but still holds its shape.

While the zucchini roasts, heat the remaining tablespoon of oil in a medium saucepan over medium heat. Sauté the onion and garlic for 2–3 minutes, until fragrant and softened.

In a small bowl, whisk the milk with the cornstarch and oregano until smooth.

Pour the milk mixture into the saucepan and simmer, stirring often, for 3–4 minutes or until the sauce thickens enough to coat the back of a spoon. Stir in the parmesan until melted and combined.

Remove the partially roasted zucchini from the oven and pour the garlic‑parmesan sauce evenly over the slices.

Top with shredded cheddar and an even layer of breadcrumbs. Return to the oven and bake for 35–40 minutes, or until the zucchini is tender and the topping is golden.

Frequently asked questions

More recipes you may like

• Crispy Smashed Potatoes
• Broccoli Chicken Pasta Casserole
• Healthy Broccoli Casserole
• Healthy Green Bean Casserole
• Baked Candied Sweet Potatoes
• Sweet Potato Casserole

If you try this recipe, please leave feedback and a rating if possible. We appreciate hearing how it turned out for you and what variations you tried. Share it with friends and family who enjoy simple, vegetable‑forward dishes.

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Easy Zucchini Casserole

By: Rena Awada

Servings: 8

Prep: 10 mins

Cook: 45 mins

Total: 55 mins

A simple zucchini casserole made with sliced zucchini, a creamy garlic‑parmesan sauce, shredded cheddar, and a crunchy breadcrumb topping. Ready in under an hour.

Equipment

• Knife
• Cutting board
• Baking dish

Ingredients

• 2 lb zucchini, sliced
• Kosher salt and ground pepper, to taste
• 3 tbsp olive oil, divided
• 1 onion, grated
• 3–4 garlic cloves, minced
• 1 cup almond milk (or 2% milk)
• 1 1/2 tbsp cornstarch
• 1/2 tsp oregano
• 1/4 cup finely grated parmesan cheese
• 1/2 cup cheddar cheese
• 1/4 cup seasoned bread crumbs

Instructions

1. Preheat the oven to 425°F (218°C).
2. Place the sliced zucchini in an oven‑safe dish and season with salt and pepper.
3. Drizzle with 2 tablespoons of oil and toss to coat. Bake 10–12 minutes until slightly softened.
4. Heat the remaining tablespoon of oil in a medium saucepan over medium heat. Sauté the onion and garlic for 2–3 minutes.
5. In a small bowl, whisk the milk with cornstarch and oregano until smooth.
6. Pour the milk mixture into the saucepan and simmer, stirring frequently, for 3–4 minutes until the sauce thickens. Stir in the parmesan.
7. Remove the roasted zucchini from the oven and pour the garlic‑parmesan sauce over it.
8. Sprinkle with cheddar and breadcrumbs. Bake 35–40 minutes more, or until the squash is tender and the top is golden.
9. Serve warm and enjoy.

Notes

• Serving size: about 1 cup.
• Add other vegetables like mushrooms or bell peppers if desired.
• Use a mix of green and yellow zucchini for color and variety.
• Substitute any milk of your choice; almond milk keeps the casserole dairy‑light.
• Use gluten‑free breadcrumbs if needed. Freshly grated cheese generally melts better than pre‑shredded.

Nutrition

Approximate per serving: Calories 138 kcal | Carbohydrates 10 g | Protein 5 g | Fat 9 g | Sodium 231 mg | Fiber 2 g. Nutrition information is an estimate and should be used as a guideline only.

Additional Info

Course: Side Dish

Cuisine: American