Cheesy Baked Meatball Casserole with Tomato Sauce

Juicy homemade meatballs baked in a rich tomato sauce and finished with a blanket of melted mozzarella—this Baked Meatballs Casserole is an easy, crowd-pleasing weeknight dinner. It’s ideal for busy evenings, travels well as meal prep, and can be frozen for later use. The recipe is low in carbohydrates yet hearty and flavorful, making it a satisfying comfort-food option that won’t leave you feeling weighed down.

Because it’s mostly hands-off once the meatballs are mixed, this casserole is perfect for hectic seasons or holiday weeks when schedules are crowded. You can form and bake the meatballs ahead of time, then simply assemble and finish the casserole when you’re ready to serve. The cheese and sauce make it irresistible for kids and adults alike, and the recipe adapts easily to what you have on hand.

If you want a few simple sides to pair with the casserole, roasted or steamed vegetables, a simple leafy salad, or a low-carb cauliflower mash are great companions. The casserole also works well alongside roasted Brussels sprouts, mashed sweet potatoes, or a fragrant cauliflower “rice” for a complete meal.

How to Make this Baked Meatballs Casserole

Prep the oven and pan

1. Preheat the oven to 400°F (200°C). Position the oven rack in the middle and butter or lightly oil a medium casserole pan. Set aside.

Make the meatballs

1. Heat 1 tablespoon of olive oil in a medium skillet over medium heat. Add 1/2 cup chopped red onion and sauté for about 5 minutes or until softened and translucent.
2. In a large bowl, combine 1 pound extra-lean ground beef, 1/4 cup seasoned keto breadcrumbs (or almond flour), 1/4 cup grated Parmesan, 1/4 cup finely chopped parsley, 1 large egg, 1 teaspoon garlic powder, 1 teaspoon onion powder, 1/2 teaspoon dried basil, and salt and freshly ground black pepper to taste. Add the sautéed onions and mix gently but thoroughly until evenly combined.
3. Form the mixture into evenly sized meatballs using a small cookie scoop or by hand. Place the meatballs in the prepared casserole dish, spacing them evenly.
4. Bake the meatballs for 15 to 20 minutes, until they are cooked through. Remove from the oven and drain any excess grease from the dish.

Top the meatballs and finish baking

1. Pour about 1 cup of tomato sauce evenly over the baked meatballs, then scatter 1 1/2 cups shredded mozzarella or your preferred melting cheese on top.
2. Return the casserole to the oven and bake for an additional 5 minutes, or until the cheese has fully melted and is slightly bubbling.

Recipe Variations

• Meat blend: Substitute or combine proteins—use half ground beef and half spicy pork sausage for extra flavor, or swap in ground turkey or chicken for a lighter option.
• Extra vegetables: Stir in cooked vegetables such as broccoli florets, cauliflower, mushrooms, or bell peppers before the final bake. The cheese helps mask veggies for picky eaters.
• Cheese alternatives: If you don’t have mozzarella, cheddar, Monterey Jack, or a mild provolone will work fine. Grate block cheese yourself for the best melting texture rather than using pre-shredded blends.
• Breadcrumb substitutes: If you don’t have seasoned keto breadcrumbs, almond flour or crushed pork rinds can be used as a low-carb binder.

Make Ahead Tip

This casserole is excellent for meal prep. After baking and cooling, divide portions into airtight containers and refrigerate for up to four days. To reheat, microwave for 1½–2 minutes depending on your microwave’s power, or reheat in a preheated 350°F (175°C) oven until warmed through. You can also freeze the casserole either before or after baking—freeze in meal-sized portions and thaw in the refrigerator before reheating.

Ingredients

• ½ cup red onion, chopped
• 1 tbsp olive oil
• 1 lb extra-lean ground beef (or a mix of beef and pork sausage)
• ¼ cup seasoned keto breadcrumbs or almond flour
• ¼ cup grated Parmesan cheese
• ¼ cup parsley, finely chopped
• 1 large egg
• 1 tsp garlic powder
• 1 tsp onion powder
• ½ tsp dried basil
• Salt and fresh ground pepper, to taste
• 1 cup tomato sauce
• 1 ½ cups mozzarella cheese, shredded, for topping
• 1 tsp fresh parsley, chopped (for garnish)

Instructions

1. Preheat the oven to 400°F (200°C) and prepare a casserole dish with butter or oil.
2. Sauté the chopped onion in olive oil over medium heat until softened, about 5 minutes.
3. In a large bowl, mix the ground beef with breadcrumbs or almond flour, Parmesan, parsley, egg, garlic powder, onion powder, dried basil, salt, and pepper. Fold in the cooked onion.
4. Shape the mixture into uniform meatballs and arrange them in the prepared casserole dish.
5. Bake the meatballs for 15–20 minutes until cooked through. Drain any excess fat from the pan.
6. Top the meatballs with tomato sauce and shredded mozzarella.
7. Return to the oven and bake an additional 5 minutes, until the cheese is fully melted and slightly bubbly.
8. Serve hot, garnished with chopped parsley if desired.

Notes and Storage

• To store: Refrigerate leftovers in an airtight container for up to 4 days.
• To reheat: Microwave single portions for 1½–2 minutes, or reheat in a 350°F (175°C) oven until warmed through.
• To freeze: Freeze meatballs before or after assembling the casserole. Freeze in airtight containers or freezer bags for up to 3 months. Thaw overnight in the refrigerator before reheating.

Nutrition Summary (approximate)

This casserole makes about six servings. An estimated nutritional profile per serving is approximately 332 calories, 38 g protein, 15 g fat, and 7 g carbohydrates. Actual values will vary based on exact ingredients and portion sizes—use this as a guideline.

This baked meatball casserole is simple, versatile, and satisfying—perfect for feeding a family, prepping meals ahead, or keeping in the freezer for quick, comforting dinners.