Zucchini Ground Beef Casserole

Zucchini ground beef casserole that’s packed with flavor, veggies, and protein! This casserole contains the delicious combination of ground beef, fresh zucchini, tomato sauce, mozzarella cheese, and quinoa! It’s easy to make and the perfect comforting weeknight dinner.

A baking dish with zucchini and ground beef casserole and a large wooden spoon in the casserole for serving.

When it comes to hearty and filling family dishes, casseroles reign supreme. They make weeknight meals a breeze and taste great as leftovers. While I love making my healthy chicken broccoli casserole, this zucchini ground beef casserole is what I put on regular rotation because it’s so easy to make and the whole family enjoys it. It’s a healthy, protein-packed twist on lasagna that’s light and flavorful, yet filling.

This casserole is also a great dish for gatherings, parties, and holidays. It’s stores well in the fridge and is easy to reheat! Best of all, it’s completely gluten free, and you only need one type of cheese to make it. And with over 33g grams of protein, it’s an absolutely delicious way to meet your protein goals!

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Ingredient Notes

Ingredients in the recipe, including ground beef, quinoa, zucchini, onion, salt and pepper, diced tomatoes, tomato sauce, garlic, basil, oregano, Italian seasoning, olive oil, and Mozzarella cheese.

Quinoa: I recommend using an organic, white quinoa because it has a delicate taste and texture, and cooks up light and fluffy. Here’s a simple way to cook it.
Ground beef: Use a 90% lean grass fed beef for the best taste and texture! Keep in mind, 90% lean has a higher percentage of protein in comparison to 80% lean.
Onion: A white or yellow onion works in this recipe.
Zucchini: The star of this casserole! Since zucchinis can vary quite a bit in size, especially if home grown, shoot for 1.5-2 pounds of zucchini total in the recipe. Cooking them beforehand draws out the excess water.
Tomato sauce: A simple 14.5 oz can of tomato sauce helps to add flavor and thicken the casserole.
Diced tomatoes: Use a low sodium 14.5 oz can of diced tomatoes. Make sure to drain the diced tomatoes before adding them to the pan.
Mozzarella cheese: The only cheese you need for this recipe! Grab pasture raised shredded Mozzarella cheese, or shred your own from a block of Mozzarella. This melts easily and adds a wonderful gooeyness to the casserole.

See recipe card for full information on ingredients and quantities.

Substitutions

Want to make this your own? Here are some quick and easy shifts you can make:

Quinoa: Not a fan of quinoa? Swap it for rice. This will reduce the overall protein content, but it’s soft and starchy!

Ground beef: Ground turkey or chicken also work great in this recipe.

Zucchini: Swap for another vegetable like yellow squash, eggplant, or bell peppers.

Mozzarella cheese: If you have another favorite cheese, use it! Monterey Jack, Cheddar, and Provolone are all great options.

Italian seasoning: Use a combination of dried oregano, basil, or thyme instead! 1 tablespoon of spice = 3 teaspoons.

How to Make Zucchini Ground Beef Casserole

1. Prep: Preheat the oven to 375°F. Grease a 9×13 inch casserole pan.

2. Cook: If not using leftovers, cook 1 cup dried quinoa on the stovetop according to the package instructions. You can also use this simple recipe to make it.

3. Brown: Heat 1 tablespoon olive oil in a large frying pan over medium heat. Add the ground beef, onions, and ½ teaspoon of the salt. Brown the meat, breaking it up with a wooden spatula as it cooks, about 5 minutes. Remove the meat from the pan and place it in the casserole dish.

4. Simmer: In the same pan, add the remaining 1 tablespoon olive oil. Add the zucchini and the remaining ½ teaspoon sea salt. Cover and cook for about 5 minutes, or until the zucchini is soft. Add the tomato sauce and drained diced tomatoes and stir to combine.

A skillet with ground beef and onions, and a skillet with the zucchini and tomato mixture cooked down.

5. Layer: Add the cooked quinoa, zucchini mixture, Italian seasoning, oregano, garlic, basil, black pepper, and 1 cup shredded mozzarella cheese to the casserole dish. Gently fold everything together until combined. Spread the mixture evenly in the casserole dish.

6. Top: Sprinkle the remaining 1 cup mozzarella cheese on top of the casserole.

How to make the recipe, including pouring the mixture into the casserole dish, and the casserole fully assembled and unbaked.

7. Bake: Bake for 25 minutes. Switch the oven to high broil and cook for 2-5 minutes to brown the cheese on top. Let it sit for five minutes before serving.

A baked zucchini and ground beef casserole in a white lasagna pan.

Cooking Tips

Make your quinoa ahead of time. I like to cook a large batch of quinoa ahead of time and use it for lunches and recipes I’m making throughout the week. For reference, 1 cup uncooked quinoa makes 3 cups cooked quinoa.
Cook the meat until just browned. Don’t overcook it as the meat and vegetables will continue to cook in the casserole in the oven.
Salt the zucchini. Make sure to salt the zucchini while you’re cooking it. Zucchini has quite a bit of water, and salting it helps it release the water so you don’t end up with a soggy casserole.

FAQs

Can I freeze this casserole for later?

Yes! If you have leftovers or are making this for meal prep, just let it cool completely, then transfer to an airtight container and store it in the freezer for up to 3 months.

Can I swap ground turkey for ground beef?

Yes! Ground beef can easily be swapped for ground turkey in most recipes. Ground turkey is a leaner meat and absorbs flavors well. It works great in casseroles and dishes that are cooked in broth or liquids like this one!

How do I cut zucchini for casseroles?

I like to cut the zucchini in halves or quarters depending on the size. My zucchinis typically get a little too big in my garden, so I slice the zucchini into 1-inch slices, then cut each slice into quarters.

Can I make the casserole ahead of time?

Yes! This casserole is great for meal prep! Assemble the casserole and cover it tightly with storage wrap. Place the dish in the refrigerator for up to 24 hours until you’re ready to bake it. The casserole will take an additional 10-15 minutes to bake out of the refrigerator.

Storage and Freezing

Storing: Casseroles typically store well in the fridge or freezer, especially when made with ground beef and vegetables like zucchini! For leftovers, store them in an airtight container in the refrigerator for up to 4 days.

Freezing: Let the casserole cool completely, then transfer it to an airtight container or freezer-safe storage bag and store it in the freezer up to 3 months. Reheating: If freezing an entire casserole, let it thaw overnight in the refrigerator. Reheat in the oven at 350°F for about 20-25 minutes, or until warm. If reheating individual portions, heat in the microwave on 10-15 second intervals until warm.

While this recipe works great in a 9×13 casserole dish, you can also make it in two 8×8-inch baking dishes! If you’re cooking for 1-2, make the recipe in two 8×8-inch pans, then throw the extra one in the freezer to have a meal made for you later.

Serving

The best thing about a casserole dish made with ground beef and zucchini is that it’s a meal on it’s own! While you don’t necessary need to serve anything extra with it, garlic bread is a traditional side that will help soak up the flavorful sauce. Looking for some other side options? Here are my favorites to pair with this dish:

Classic House Salad – Light, crisp, and a classic!
Rainbow Roasted Vegetables – These roasted vegetable are flavorful and gorgeous. They go with anything!
Crispy Roasted Sweet Potatoes – These small diced sweet potatoes are perfectly crisp. A great starchy alternative to bread!
Instant Pot Brown Jasmine Rice – I love rice with just about anything—especially tomato based dishes. Making a large batch in the Instant Pot is so easy!

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