Vegetarian Casserole – Cozy, Flavorful, and Weeknight-Friendly

If you want something warm, hearty, and easy to throw together, this vegetarian casserole hits the spot. It’s packed with colorful veggies, tender beans, and a creamy, cheesy topping that feels comforting without being heavy. The best part?

It uses simple pantry staples and flexible ingredients, so you can make it your own. This is the kind of recipe you’ll keep on rotation, whether you’re feeding a family or meal-prepping for the week.

Print Recipe

Vegetarian Casserole - Cozy, Flavorful, and Weeknight-Friendly

Prep Time15 minutes mins

Cook Time35 minutes mins

Total Time50 minutes mins

Servings: 6 servings

Ingredients

• 2 tablespoons olive oil
• 1 medium yellow onion, diced
• 3 cloves garlic, minced
• 1 red bell pepper, diced
• 2 cups chopped zucchini (about 2 small)
• 1 cup sliced mushrooms
• 1 cup corn kernels (fresh, canned, or frozen)
• 1 can (15 oz) black beans, drained and rinsed
• 1 can (14.5 oz) diced tomatoes, drained
• 1 cup cooked quinoa or brown rice
• 1 cup tomato sauce or marinara
• 1 teaspoon dried oregano
• 1 teaspoon smoked paprika
• 1/2 teaspoon ground cumin
• 1/2 teaspoon chili flakes (optional)
• Salt and black pepper to taste
• 1 cup shredded cheddar or mozzarella (or a mix)
• 1/4 cup grated Parmesan (optional)
• Fresh parsley or cilantro, chopped, for garnish

Instructions

• Preheat your oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish.
• Warm the olive oil in a large skillet over medium heat.Add the onion and cook until translucent, about 3–4 minutes. Stir in the garlic and cook 30 seconds, until fragrant.
• Add the bell pepper, zucchini, and mushrooms. Cook, stirring occasionally, until the vegetables soften and release their moisture, 6–8 minutes.
• Stir in the corn, black beans, and drained tomatoes.Season with oregano, smoked paprika, cumin, chili flakes (if using), salt, and pepper. Cook 2–3 minutes to blend the flavors.
• Fold in the cooked quinoa or brown rice and the tomato sauce. Taste and adjust seasoning.The mixture should be well-seasoned and slightly saucy.
• Transfer the mixture to the prepared baking dish. Sprinkle evenly with shredded cheese and Parmesan, if using.
• Bake for 18–22 minutes, until the cheese is melted and bubbling and the casserole is heated through.
• Let it rest for 5 minutes. Garnish with chopped parsley or cilantro.Serve warm.

What Makes This Recipe So Good

• Balanced and satisfying: Protein-rich beans, fiber-filled veggies, and a bit of cheese make it filling without meat.
• Flexible: Swap in what you have—frozen veggies, different beans, or your favorite cheese.
• Make-ahead friendly: Assemble earlier in the day and bake when you’re ready to eat.
• Great leftovers: It reheats well and tastes even better the next day.
• Budget-conscious: Uses affordable ingredients and stretches to feed a crowd.

Ingredients

• 2 tablespoons olive oil
• 1 medium yellow onion, diced
• 3 cloves garlic, minced
• 1 red bell pepper, diced
• 2 cups chopped zucchini (about 2 small)
• 1 cup sliced mushrooms
• 1 cup corn kernels (fresh, canned, or frozen)
• 1 can (15 oz) black beans, drained and rinsed
• 1 can (14.5 oz) diced tomatoes, drained
• 1 cup cooked quinoa or brown rice
• 1 cup tomato sauce or marinara
• 1 teaspoon dried oregano
• 1 teaspoon smoked paprika
• 1/2 teaspoon ground cumin
• 1/2 teaspoon chili flakes (optional)
• Salt and black pepper to taste
• 1 cup shredded cheddar or mozzarella (or a mix)
• 1/4 cup grated Parmesan (optional)
• Fresh parsley or cilantro, chopped, for garnish

Instructions

1. Preheat your oven to 375°F (190°C). Lightly grease a 9×13-inch baking dish.
2. Warm the olive oil in a large skillet over medium heat.

   Add the onion and cook until translucent, about 3–4 minutes. Stir in the garlic and cook 30 seconds, until fragrant.

3. Add the bell pepper, zucchini, and mushrooms. Cook, stirring occasionally, until the vegetables soften and release their moisture, 6–8 minutes.
4. Stir in the corn, black beans, and drained tomatoes.

   Season with oregano, smoked paprika, cumin, chili flakes (if using), salt, and pepper. Cook 2–3 minutes to blend the flavors.

5. Fold in the cooked quinoa or brown rice and the tomato sauce. Taste and adjust seasoning.

   The mixture should be well-seasoned and slightly saucy.

6. Transfer the mixture to the prepared baking dish. Sprinkle evenly with shredded cheese and Parmesan, if using.
7. Bake for 18–22 minutes, until the cheese is melted and bubbling and the casserole is heated through.
8. Let it rest for 5 minutes. Garnish with chopped parsley or cilantro.

   Serve warm.

How to Store

• Refrigerate: Cool completely, then cover tightly. Keeps 4–5 days.
• Freeze: Portion into airtight containers. Freeze up to 2 months.

  Thaw overnight in the fridge.

• Reheat: Microwave individual servings 1–2 minutes, or bake covered at 350°F (175°C) for 15–20 minutes until hot.

Health Benefits

• High in fiber: Beans, veggies, and whole grains support digestion and steady energy.
• Plant-based protein: Beans and quinoa help keep you full and support muscle health.
• Micronutrient-rich: Peppers, zucchini, tomatoes, and mushrooms bring vitamins A, C, K, folate, and antioxidants.
• Customizable for dietary needs: Easy to make gluten-free or dairy-free with simple swaps.

Pitfalls to Watch Out For

• Watery casserole: Drain tomatoes well and cook veggies until most moisture evaporates before assembling.
• Under-seasoning: Taste as you go. The grains and beans need enough salt and spices.
• Overcooking cheese: Bake just until melted and bubbly to avoid a tough top.
• Uneven heat: If baking from cold, add 5–10 minutes and cover with foil for the first half of baking.

Variations You Can Try

• Mexican-inspired: Use pinto beans, add 1 teaspoon taco seasoning, and top with pepper jack and sliced jalapeños.
• Mediterranean: Swap tomato sauce for crushed tomatoes, add olives, artichokes, spinach, and feta.
• Italian comfort: Use marinara, add chopped kale and white beans, and top with mozzarella and Parmesan.
• Dairy-free: Skip cheese or use a vegan melt. Add a crunchy topping of olive-oil tossed breadcrumbs.
• Extra-protein: Add more beans or a cup of lentils (pre-cooked) and a sprinkle of hemp seeds before serving.

FAQ

Can I make this casserole ahead of time?

Yes.

Assemble up to 24 hours in advance, cover, and refrigerate. When ready, bake at 375°F (190°C), adding 5–10 extra minutes if it’s cold.

What can I use instead of quinoa?

Brown rice, farro, couscous, or small pasta all work. Just cook them first and adjust seasoning to taste.

How do I make it spicier?

Add chili flakes, diced jalapeño, a splash of hot sauce, or use pepper jack cheese for a kick.

Is this recipe gluten-free?

It can be.

Use gluten-free grains like quinoa or rice and check labels on tomato sauce and cheese.

Can I add more vegetables?

Absolutely. Broccoli, cauliflower, spinach, or sweet potato are great. Pre-cook harder veggies so everything finishes at the same time.

What cheese melts best?

Mozzarella and Monterey Jack melt beautifully.

For stronger flavor, mix in sharp cheddar or a little provolone.

Wrapping Up

This vegetarian casserole is simple, adaptable, and deeply satisfying. It’s the kind of dish that makes weeknights easier and leftovers exciting. Keep the base the same, then tweak the add-ins to match your mood and pantry.

A warm, bubbly pan of comfort is never far away.