Sunday Baked Vegetable Casserole

Name: Sunday Baked Vegetable Casserole
Prep time: 20 min
Cook time: 45 min
Total time: 1 h 5 min
Yield: 6 servings
Ingredients: 2 medium zucchini, sliced; 1 red bell pepper, chopped; 1 yellow bell pepper, chopped; 2 cups fresh spinach; 1 onion, chopped; 3 tablespoons butter; 3 tablespoons all-purpose flour; 2 cups milk; 1 teaspoon garlic powder; Salt and pepper to taste; 1 cup shredded mozzarella cheese; 1/2 cup breadcrumbs; 1 tablespoon olive oil; 1 teaspoon Italian seasoning

Highlighted under: Baking & Desserts

I love preparing a comforting Sunday Baked Vegetable Casserole that warms the soul while gathering the family around the dinner table. This dish not only incorporates a medley of fresh vegetables but also brings together rich flavors with a cheesy topping, making it an instant hit. Each bite is packed with nutrition, and it's so easy to customize based on what I have on hand. Whether it’s the creamy béchamel at the bottom or the slightly crispy top, this casserole is bound to become a staple in your home too!

Created by

Marley Quinn

Last updated on 2026-01-13T21:13:14.032Z

When I first tried making a vegetable casserole, I was surprised at how simple it was to create something so delicious. I experimented with various vegetables and settled on a blend of zucchini, bell peppers, and spinach, which adds a freshness to the dish. Topping it with a mix of cheese and breadcrumbs gives it a delightful texture.

What I found makes this casserole even better is letting it rest for a few minutes after baking. That little time allows the flavors to meld beautifully, resulting in a comforting dish that’s perfect for any family gathering or relaxed Sunday dinner.

        Why You'll Love This Recipe
        A colorful medley of seasonal veggies that brighten your meal
Creamy sauce and crispy topping make for a delightful texture
Perfect for meal prepping or enjoying leftovers throughout the week

      

Choosing the Right Vegetables

The beauty of the Sunday Baked Vegetable Casserole lies in its flexibility with vegetables. While zucchini, bell peppers, onion, and spinach shine in this recipe, feel free to substitute with seasonal options like eggplant, broccoli, or asparagus. Just keep in mind to cut your vegetables into uniform sizes to ensure even cooking. Also, consider how strong flavors can influence your dish; for instance, if using broccoli, blanch it beforehand to soften its robust texture before mixing it into the casserole.

Texture is also crucial for a satisfying casserole. For instance, if you're introducing vegetables that tend to release a lot of moisture, such as mushrooms or tomatoes, consider sautéing them longer to evaporate excess liquid. This will prevent your casserole from becoming soggy. Additionally, crisper vegetables like bell peppers or carrots can be added later in the cooking process to maintain a bit of crunch.

Mastering the Béchamel Sauce

Béchamel sauce is the heart of this casserole, giving it a creamy base that ties everything together. The key to a smooth and luscious béchamel is to whisk continuously while gradually adding the milk. This prevents lumps from forming and ensures a silky texture. If lumps do form, consider using a hand blender to quickly remedy the texture before baking.

To elevate the flavor of your béchamel, try infusing it with herbs or spices while cooking. A pinch of nutmeg can enhance the depth of flavor significantly. If you're looking for a dairy-free option, unsweetened almond milk works well in place of regular milk, while a cornstarch slurry can replace flour for a gluten-free version.

Serving and Storing Leftovers

Once your casserole is baked to golden perfection, let it cool for a few minutes before serving. This helps the layers set, making it easier to serve neat portions. This dish is ideal for family potlucks or as a main dish at gatherings—pair it with a fresh green salad to balance its richness.

For leftovers, store them in an airtight container in the fridge for up to four days. You can also freeze portions for up to three months; just ensure to cool the casserole completely before wrapping it tightly in foil or plastic wrap. To reheat, place it in a preheated oven at 350°F (175°C) for about 20-30 minutes until heated through, which helps retain its texture better than microwaving.

Ingredients

Gather these ingredients to make your casserole come alive!

Vegetables

2 medium zucchini, sliced
1 red bell pepper, chopped
1 yellow bell pepper, chopped
2 cups fresh spinach
1 onion, chopped

Sauce

3 tablespoons butter
3 tablespoons all-purpose flour
2 cups milk
1 teaspoon garlic powder
Salt and pepper to taste

Topping

1 cup shredded mozzarella cheese
1/2 cup breadcrumbs
1 tablespoon olive oil
1 teaspoon Italian seasoning

Now that you have your ingredients, let’s cook!

Instructions

Follow these simple steps for a delicious casserole.

Prepare the Vegetables

Preheat your oven to 350°F (175°C). In a large skillet, sauté the onion, zucchini, and bell peppers until softened, about 5-7 minutes. Stir in the spinach and cook until wilted, then set aside.

Make the Sauce

In the same skillet, melt butter over medium heat. Whisk in the flour and cook for about a minute. Gradually pour in the milk while whisking, and cook until the sauce thickens.

Add garlic powder, salt, and pepper.

Combine and Bake

In a large baking dish, mix the sautéed vegetables with the sauce. Top with mozzarella cheese, breadcrumbs mixed with olive oil and Italian seasoning. Bake for 30-35 minutes or until the top is golden brown.

Let the casserole rest for a few minutes before serving. Enjoy!

Pro Tips

Feel free to swap in your favorite vegetables or add some cooked protein like chicken or beans for added heartiness.

Tips for Customizing Your Casserole

The Sunday Baked Vegetable Casserole is incredibly versatile. Think about swapping out the mozzarella cheese for a sharper cheddar or a creamy goat cheese to change the flavor profile significantly. You could also add cooked quinoa or lentils for extra protein, making it even more filling. Experimenting with different cheeses or adding fresh herbs like basil or parsley can enhance its freshness and personality.

If you're looking to reduce the calories, consider using less cheese or substituting with a lighter cheese option. Alternatively, a sprinkle of nutritional yeast can give a cheesy flavor without the heaviness, perfect for vegan diets. The cooking time may need adjustments, so keep an eye on it while baking!

Troubleshooting Common Issues

If your casserole seems watery after baking, it could be due to excess liquid from the vegetables. To combat this next time, either cook your vegetables longer before mixing them with the sauce to let some moisture escape or use a thicker béchamel by increasing the flour slightly. Remember to drain any additional moisture from ingredients like frozen spinach before sautéing.

Another issue could arise if your casserole lacks depth of flavor. If you find the final product bland, it’s often a sign you need more seasoning. Tasting your béchamel before adding it to the vegetables is a good practice. You can easily adjust with more salt, pepper, or even a dash of hot sauce for a kick!

Questions About Recipes

→ Can I make this casserole ahead of time?

Absolutely! Prepare the casserole and cover it tightly. Refrigerate overnight and simply bake it when you're ready.

→ What can I substitute for milk in the sauce?

You can use non-dairy alternatives like almond milk or oat milk, and it will still work well.

→ Is this recipe gluten-free?

To make this recipe gluten-free, simply use a gluten-free flour for the sauce and gluten-free breadcrumbs.

→ How long will leftovers keep in the fridge?

Leftovers can be stored in the refrigerator for up to 3 days. Reheat in the oven or microwave.