45-Minute Cheesy Ground Beef Zucchini Casserole

This cheesy ground beef zucchini casserole is a weeknight dinner that comes together fast and tastes like a no-noodle lasagna.

Zucchini slices soften into a rich beef and tomato sauce, then everything gets baked under a golden layer of melted mozzarella. It’s hearty, low on fuss, and keeps you full without feeling heavy.

What Makes This Zucchini Casserole Work

The beef sauce is a simple mix of onions, garlic, and Italian seasoning, so it reminds me of a lazy Sunday meat sauce but comes together on a Tuesday. The zucchini holds its shape without getting watery, because we salt it first.

That quick salt step draws out extra moisture, so you get tender coins instead of a soupy mess. Then the cheese on top gets bubbly and brown in the oven, which is the whole point of a casserole in my book.

I keep coming back to this one when I have too much zucchini and not enough time. It’s sturdy enough to serve as is, and leftovers reheat beautifully.

Ingredients

• 1 lb ground beef: 80/20 keeps it flavorful, but you can drain excess fat.
• 3 medium zucchini (about 1 1/2 lbs): sliced into 1/4-inch rounds; salting them first draws out moisture so the casserole isn’t watery.
• 1 medium yellow onion: diced; yellow onion gives a sweet base.
• 3 cloves garlic: minced; fresh is best.
• 1 can (15 oz) tomato sauce: use plain tomato sauce, not pasta sauce with added sugar.
• 2 tsp Italian seasoning: a blend of oregano, basil, and thyme.
• 1 tsp salt, divided: some for the zucchini, the rest for the sauce.
• 1/2 tsp black pepper: freshly ground.
• 2 cups shredded mozzarella cheese: whole-milk low-moisture mozzarella melts best.
• 1/4 cup grated Parmesan cheese: adds a salty, nutty top.
• Fresh basil: optional, for garnish.

Variations / Substitutions

• Ground Turkey: swap for the beef; use a little olive oil when browning so it doesn’t dry out.
• Dairy-Free: use a good melting vegan mozzarella and skip the Parmesan.
• Add Heat: stir 1/2 teaspoon red pepper flakes into the meat while it cooks.
• Extra Veggies: toss in sliced mushrooms or bell peppers with the onions.
• Fresh Herbs: stir a handful of chopped basil into the sauce right before layering.

Steak Chili goes perfectly with this casserole for a cozy meal.

How to Make Ground Beef Zucchini Casserole

Step 1: Salt the Zucchini

Place the 3 medium sliced zucchini in a colander and toss with 1/2 teaspoon of the salt. Let it sit for 15 minutes to draw out the moisture, then pat the rounds very dry with a clean kitchen towel.

The zucchini will look a little wilted and release beads of water on its surface. Drying them well stops the casserole from turning into a soup.

Step 2: Brown the Beef and Aromatics

Heat a large skillet over medium-high heat. Add the 1 lb ground beef and cook, breaking it up with a spoon, until no longer pink, about 6 minutes. Drain off most of the fat, leaving about a tablespoon for flavor.

Add the diced onion to the pan and cook until it turns translucent and just starts to brown at the edges, about 4 more minutes. Stir in the minced garlic and cook for 30 seconds until fragrant.

Step 3: Simmer the Sauce

Pour in the 15 oz can of tomato sauce, the 2 tsp Italian seasoning, the remaining 1/2 tsp salt, and the 1/2 tsp black pepper. Stir everything together and bring to a gentle simmer over medium heat. Let it cook for 5 minutes, stirring occasionally, so the flavors meld and the sauce thickens slightly.

You’ll see the sauce turn a deep red and smell the herbs waking up. That little simmer makes the whole casserole taste like it cooked for hours.

Step 4: Layer the Casserole

Preheat your oven to 375°F (190°C) with a rack in the middle. Spread a thin layer of the meat sauce in the bottom of a 9×13-inch baking dish. Arrange half of the dried zucchini rounds in a single layer, overlapping slightly. Spoon half of the remaining sauce over the zucchini, then sprinkle with 1 cup of the shredded mozzarella.

Repeat with the rest of the zucchini, the remaining sauce, and top with the last cup of mozzarella and all of the grated Parmesan. At this point, the dish should look like a lasagna, with cheese completely covering the sauce.

Step 5: Bake and Broil the Casserole

Slide the dish into the preheated oven and bake for 25 minutes, until the sauce is bubbling and the cheese has melted. Switch the oven to broil and watch closely for 2 to 3 minutes until the top is golden and crisp in spots.

When you pull it out, the casserole will be molten and fragrant. Let it sit for 5 minutes so the juices settle, then scoop generous portions onto plates. Tear fresh basil over the top right before you dig in.

Tips for the Best Zucchini Casserole

• Choose firm, small to medium zucchini.: Large ones have more seeds and water, so they break down faster.
• Don’t skip the broil at the end.: That extra minute of high heat gives the cheese crispy, golden edges that make the dish.
• Use whole-milk mozzarella.: The low-moisture, whole-milk kind melts into a creamy blanket rather than turning rubbery.
• Make it ahead.: You can assemble the casserole, cover, and refrigerate for up to 24 hours before baking. Add 10 extra minutes to the bake time if going in cold.
• Stir in a can of drained cannellini beans: to the sauce for a heartier casserole.

Bake times by dish size:

Storing and Reheating Leftovers

• Refrigerate: Store leftovers in an airtight container in the refrigerator for up to 4 days. The flavors get even better overnight.
• Reheating: Reheat individual portions in the microwave until hot, or warm the whole dish in a 350°F oven for 15 minutes. If the top looks dry, sprinkle a little extra cheese before reheating.

What to Serve with Ground Beef Zucchini Casserole

A crisp green salad dressed with lemon and olive oil offsets the richness of the cheese and beef. If you want something to mop up the sauce, warm garlic bread does the trick. A red grape juice rounds out the plate.

Frequently Asked Questions

Can I use frozen zucchini slices?

Yes. Thaw them completely, then press out as much liquid as you can before layering. The texture will be softer but still works.

Can I freeze this casserole?

Absolutely. Bake it, cool completely, then wrap tightly and freeze for up to 3 months. Thaw in the fridge overnight and reheat in the oven.

Is this casserole gluten-free?

The ingredients are naturally gluten-free. Just double-check that your tomato sauce and Italian seasoning don’t contain hidden wheat.

Can I add pasta to make it more filling?

You can. Stir 2 cups of cooked short pasta, like penne, into the meat sauce before layering. You may need a little extra tomato sauce to keep it saucy.

Ground Beef Zucchini Casserole Recipe

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Prep Time 15 minutes mins

Cook Time 30 minutes mins

Total Time 45 minutes mins

Servings: 6 servings

Calories: 280

Ingredients Method Notes

Ingredients

  

• 1 lb ground beef
• 3 medium zucchini (about 1 1/2 lbs), sliced into 1/4-inch rounds
• 1 medium yellow onion, diced
• 3 cloves garlic, minced
• 1 can (15 oz) tomato sauce
• 2 tsp Italian seasoning
• 1 tsp salt, divided
• 1/2 tsp black pepper
• 2 cups shredded mozzarella cheese
• 1/4 cup grated Parmesan cheese
• Fresh basil, for garnish (optional)

Method

 

1. Salt the zucchini: Toss sliced zucchini with 1/2 teaspoon salt, let drain 15 minutes, then pat very dry.
2. Brown the beef: Cook ground beef in a skillet over medium-high heat until no pink remains, about 6 minutes. Drain off excess fat, leaving a tablespoon. Add onion and cook until soft, 4 minutes, then add garlic and cook 30 seconds.
3. Simmer the sauce: Stir in tomato sauce, Italian seasoning, remaining 1/2 teaspoon salt, and pepper. Bring to a simmer and cook 5 minutes, stirring occasionally.
4. Layer the casserole: Preheat oven to 375°F (190°C). Spread a thin layer of sauce in a 9×13-inch dish. Layer half the zucchini, half the remaining sauce, and 1 cup mozzarella. Repeat with remaining zucchini, sauce, and top with the last 1 cup mozzarella and all of the Parmesan.
5. Bake and broil: Bake for 25 minutes until bubbly, then broil 2 to 3 minutes until the top is golden and crisp. Let rest 5 minutes, then scoop onto plates and top with fresh basil.

Notes

The 15-minute drain for the zucchini is built into the timeline, but you can get the beef going while it sits to save time. For a crispier top, broil an extra minute.