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 cups chopped zucchini; 1 cup diced bell peppers; 1 cup spinach leaves; 1 cup chopped tomatoes; 1 cup sliced mushrooms; 2 cups cooked quinoa or rice; 1 cup shredded cheese (mozzarella or cheddar); 1 cup milk or plant-based milk; 2 large eggs; 1 teaspoon garlic powder; 1 teaspoon onion powder; Salt and pepper to taste

Highlighted under: Comfort Food

I always look forward to Sundays because they give me a chance to unwind and share a hearty meal with family. This Sunday Baked Vegetable Casserole has become a tradition in our household, brimming with colorful vegetables and rich flavors. Each time I make it, I experiment with different seasonal veggies, which adds a delightful twist to the dish. The creamy sauce holds everything together, making each bite comforting and satisfying. I can't wait for you to try it at your next gathering!

Created by

Rosalie Mitchell

Last updated on 2026-01-13T22:16:12.612Z

Last week, while preparing this casserole, I decided to use a mix of zucchini, bell peppers, and spinach based on what I had in the fridge. I roasted the vegetables first, which brought out their natural sweetness and added a lovely caramelization. The result was an explosion of flavor in every layer, and my family couldn't get enough of it!

One tip I've discovered is to let the casserole rest for a few minutes before serving. This allows the layers to set and makes it easier to slice. Trust me; it’s worth the wait!

        Why You'll Love This Recipe
        A delightful blend of seasonal vegetables to brighten your plate
Creamy, cheesy sauce that brings everything together
Perfect for meal prepping or serving a crowd

      

Ingredient Versatility

One of the best aspects of this Sunday Baked Vegetable Casserole is its versatility. You can easily swap in your favorite seasonal vegetables based on availability or personal preference. For instance, during the fall, adding roasted butternut squash or sweet potatoes would introduce a warm sweetness, while summertime might call for fresh corn or crispy snap peas. Just be mindful of cooking times; denser vegetables may need a bit longer to soften before mixing them into the casserole.

Herbs can also play a significant role in elevating the dish's flavor profile. Consider incorporating fresh basil or thyme to enhance the overall taste. If you're working with drier herbs like oregano, add them early in the sautéing process to release their essential oils. This infusion will make your casserole aromatic and deeply flavorful.

Perfecting the Creamy Sauce

The creamy sauce binds all the ingredients and adds an appealing richness to the casserole. Using a blend of milk and eggs helps ensure a tender, custard-like texture. If you prefer a plant-based option, substitute dairy milk with almond or oat milk. Just be aware that these alternatives can alter the thickness slightly, so you may want to add a touch of cornstarch or flour to achieve the same smooth consistency.

When layering the shredded cheese, feel free to experiment with different varieties. A sharp cheddar will add a bold flavor, while mozzarella offers a beautiful meltiness. If you want to keep the dish lighter, consider using a reduced-fat cheese or a dairy-free substitute that melts well. I find that a combination of cheese delivers the best results.

Make-Ahead Tips and Storage

For busy weeks, you can prepare this casserole in advance. Assemble the components, cover them with plastic wrap, and refrigerate for up to 24 hours before baking. This allows the flavors to meld beautifully. If you'd like to freeze, assemble the casserole without baking it and store it in an airtight container for up to three months. When ready to enjoy, thaw it overnight in the refrigerator and then bake as directed, adding an extra 10 minutes to the cooking time if it's still cool from the fridge.

To reheat leftovers, simply slice a portion and microwave it on medium power for about 2-3 minutes, or until warmed through. Alternatively, you can place the leftover casserole in the oven at 350°F (175°C) for about 15-20 minutes, covering it with foil to retain moisture. This method helps revive the creaminess and texture of the dish, making it almost as good as fresh.

Ingredients

Gather the following ingredients to prepare your casserole:

Vegetables

2 cups chopped zucchini
1 cup diced bell peppers
1 cup spinach leaves
1 cup chopped tomatoes
1 cup sliced mushrooms

Casserole Base

2 cups cooked quinoa or rice
1 cup shredded cheese (mozzarella or cheddar)
1 cup milk or plant-based milk
2 large eggs
1 teaspoon garlic powder
1 teaspoon onion powder
Salt and pepper to taste

Make sure to adjust the seasoning according to your taste!

Instructions

Follow these simple steps to create your casserole:

Preheat the Oven

Preheat your oven to 375°F (190°C).

Prepare the Vegetables

In a large skillet, sauté the zucchini, bell peppers, spinach, tomatoes, and mushrooms in a little olive oil over medium heat until softened, about 5-7 minutes.

Mix the Casserole Base

In a large mixing bowl, combine the cooked quinoa or rice, sautéed vegetables, shredded cheese, milk, eggs, garlic powder, onion powder, salt, and pepper. Stir until well mixed.

Transfer to Baking Dish

Pour the mixture into a greased baking dish, spreading it out evenly.

Bake

Bake in the preheated oven for 30-35 minutes, until the top is golden and bubbly.

Let It Rest

Once done, remove from the oven and let it rest for 10 minutes before slicing.

Serve warm and enjoy your delightful vegetable casserole!

Pro Tips

For added flavor, consider adding herbs like basil or thyme. You can also top your casserole with breadcrumbs for a crunchy texture.

Serving Suggestions

This baked vegetable casserole can stand alone as a hearty vegetarian main dish, but it also pairs beautifully with a light salad or a serving of crusty bread. A simple arugula salad with lemon vinaigrette complements the rich flavors while adding a refreshing contrast. Moreover, if you're serving a larger crowd, consider adding a protein like grilled chicken or baked tofu on the side to round out the meal.

Presentation can enhance your dining experience as well. Garnish the casserole with fresh herbs, such as parsley or a sprinkle of extra cheese right before serving. A drizzle of olive oil can also add a nice touch, giving it a glossy look and enhancing flavor. I always appreciate a bit of color—it makes the dish even more inviting.

Troubleshooting Common Issues

If you find that your casserole turns out too dry, it may have been baked for too long or not had enough liquid in the mix. To avoid this, keep an eye on it during the last few minutes of baking and adjust the cooking time according to your oven's performance, as some can run hotter than others. A simple fix is to add a splash of milk on top before covering and returning it to the oven for a few extra minutes.

On the other hand, if your casserole is too wet, it could be due to excessive moisture from the vegetables. To counteract this, try sautéing the veggies for a few extra minutes to release more water before mixing them into the base. Alternatively, you can elevate the dish by baking it uncovered for the last 10 minutes to help evaporate any excess liquid.

Questions About Recipes

→ Can I use frozen vegetables for this casserole?

Yes, frozen vegetables can be substituted. Just ensure they are thawed and drained before adding them to the mixture.

→ Can I make this casserole vegan?

Absolutely! Use plant-based milk, vegan cheese, and flax eggs instead of regular eggs.

→ How do I store leftovers?

Store any leftovers in an airtight container in the refrigerator for up to 3 days. Reheat in the oven or microwave.

→ Can I add meat to this casserole?

Yes! Feel free to add cooked chicken, sausage, or beef for added protein.