This Cheesy Zucchini Pizza Casserole is the ultimate make-ahead dinner for macro-friendly meal prep. Loaded with zucchini, marinara, and cheese, it's a quick high-protein casserole perfect for healthy family dinners.

Ingredients

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Instructions

Step 1

Preheat your oven to 400°F (200°C). While the oven heats, prepare the zucchini. Wash the zucchinis thoroughly and trim off the ends. Using a sharp knife or a mandoline slicer, cut them into uniform 1/4-inch thick rounds. Uniform thickness is crucial for even cooking; if slices are too thick, they won’t soften properly, and if too thin, they may turn mushy. Place the slices in a large bowl and toss with 1 tablespoon olive oil, 1/2 teaspoon salt, and 1/4 teaspoon black pepper. Spread them in a single layer on two baking sheets lined with parchment paper. Roast for 10 minutes, flipping halfway, until they are slightly tender and have released some moisture. This step concentrates the zucchini flavor and prevents the casserole from becoming watery. Remove from oven and set aside. Leave the oven on.

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Step 2

While the zucchini roasts, prepare the other vegetables and the sauce. Dice the green bell pepper into small, even pieces (about 1/4-inch). Slice the mushrooms thinly. If using fresh mushrooms, wipe them clean with a damp paper towel—never rinse them, as they absorb water and become soggy. For the sauce, pour the marinara into a medium bowl and stir in the dried oregano, garlic powder, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon black pepper, and red pepper flakes if using. Taste and adjust seasonings—the sauce is the backbone of the pizza flavor, so it should be robust and well-seasoned. If your marinara is acidic, a pinch of sugar can balance it, but for a low-carb version, omit the sugar.

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Step 3

Now it’s time to assemble the casserole. Lightly grease a 9×13-inch baking dish with cooking spray or olive oil. Spread a thin layer of the seasoned marinara (about 1/2 cup) on the bottom of the dish. This prevents sticking and adds moisture to the base. Arrange half of the roasted zucchini rounds in an even layer over the sauce, slightly overlapping them like shingles. Spoon half of the remaining sauce over the zucchini, spreading gently. Sprinkle half of the diced bell pepper, half of the sliced mushrooms, and half of the pepperoni over the sauce. Then top with half of the mozzarella and half of the Parmesan. Repeat the layers: remaining zucchini, remaining sauce, remaining vegetables and pepperoni, and finally the remaining mozzarella and Parmesan. The top layer should be cheese-heavy to create that irresistible golden crust.

Step 4

Bake the casserole uncovered in the preheated oven for 20-25 minutes, or until the cheese is bubbly and golden brown. For an extra-crispy top, switch the oven to broil for the last 2-3 minutes, watching carefully to prevent burning. The casserole is done when the internal temperature reaches 165°F (74°C) and the edges are bubbling. Let it rest on a wire rack for 10 minutes before cutting. This resting period allows the casserole to set, making it easier to slice into neat portions. Garnish with fresh basil leaves just before serving.

Step 5

For meal prep, allow the casserole to cool completely to room temperature (about 30 minutes). Then divide it into 6 airtight meal prep containers. Each portion should be about 1/6 of the casserole. Store in the refrigerator for up to 5 days, or freeze for up to 3 months. To reheat, microwave on high for 2-3 minutes (stirring halfway) or bake at 350°F for 15 minutes until hot. The casserole reheats beautifully, making it a perfect grab-and-go lunch or dinner.

For best results

  • To prevent a watery casserole, salting and roasting the zucchini beforehand is non-negotiable. Zucchini is over 90% water, and if you skip this step, the casserole will become soupy. After roasting, you can also pat the slices with paper towels to remove excess moisture. For even better results, salt the raw zucchini slices and let them sit in a colander for 15 minutes, then blot dry before roasting. This double-sweat method ensures maximum water removal and a firm texture.
  • Choose a high-quality marinara sauce with no added sugars for a lower-carb, cleaner flavor profile. Look for sauces with simple ingredients: tomatoes, olive oil, garlic, and herbs. Rao's Homemade or Victoria are excellent options. If you prefer a spicier sauce, add extra red pepper flakes or a dash of cayenne. You can also make your own quick marinara by simmering crushed tomatoes with garlic, oregano, and a pinch of salt for 10 minutes.
  • For the cheesiest top, use a mix of low-moisture part-skim mozzarella and freshly grated Parmesan. Pre-shredded cheeses often contain anti-caking agents that prevent smooth melting. Grating your own cheese from a block ensures superior melt and flavor. For a richer taste, substitute provolone or fontina for part of the mozzarella. If you're dairy-free, use a high-quality plant-based mozzarella that melts well, but note that the texture and browning may differ.
  • Turkey pepperoni is a great way to boost protein while reducing fat and calories. It crisps up beautifully in the oven. For a vegetarian version, use plant-based pepperoni or omit it entirely and add extra mushrooms and bell peppers. You can also swap pepperoni with cooked Italian sausage (chicken or turkey) for a heartier casserole. Brown the sausage first and drain excess fat before layering.
  • To make this casserole keto-friendly, use a low-carb marinara (check labels—many have 4-6g net carbs per serving) and reduce the bell pepper (higher in carbs) or substitute with more zucchini and mushrooms. The cheese and pepperoni are naturally low-carb. Each serving will then have around 8-10g net carbs, fitting perfectly into a keto meal plan.
  • Meal prep containers: Use glass containers with airtight lids for best results. Glass doesn't absorb odors or stain like plastic, and it reheats evenly. Portion the casserole while it's still slightly warm—if it cools completely in the dish, it may stick. For freezing, wrap each container tightly with plastic wrap and then foil to prevent freezer burn. Thaw overnight in the refrigerator before reheating.

Variations

  • Vegetarian Zucchini Pizza Casserole: Omit the pepperoni and add 1 cup of sliced black olives, 1 cup of artichoke hearts (quartered), and an extra 1/2 cup of mushrooms. For a protein boost, stir in 1 cup of cooked lentils or crumbled firm tofu seasoned with Italian herbs. The lentils add a meaty texture and pair well with the marinara. For a vegan version, use dairy-free cheese and a vegan pepperoni alternative.
  • Meat Lover's Zucchini Pizza Casserole: In addition to pepperoni, add 1/2 pound of cooked and crumbled Italian sausage (casings removed) and 1/2 cup of diced cooked bacon. Brown the sausage and bacon together, drain excess fat, and layer them in the casserole. This variation is higher in protein and fat, making it more satiating. For a leaner option, use chicken or turkey sausage.
  • Low-Carb/Keto Zucchini Pizza Casserole: Use a low-carb marinara (like Rao's) and replace the bell pepper with additional zucchini or spinach. Add 1/2 cup of ricotta cheese mixed with an egg for a creamy layer—this adds richness without many carbs. For extra fat, drizzle olive oil over the top before baking. Each serving will have about 8g net carbs, perfect for keto dieters.
  • Spicy Southwest Zucchini Pizza Casserole: Swap the pepperoni for cooked ground beef or turkey seasoned with chili powder, cumin, and smoked paprika. Use a salsa verde or enchilada sauce instead of marinara. Top with a blend of Monterey Jack and cheddar cheese, and garnish with fresh cilantro and sliced jalapeños. This variation gives a Tex-Mex twist with bold flavors.

Nutrition

  • Calories295 kcal
  • Total Fat16g
  • Saturated Fat7g
  • Cholesterol55mg
  • Sodium820mg
  • Total Carbohydrates14g
  • Dietary Fiber3g
  • Sugars8g
  • Protein24g

Common Questions

Can I use frozen zucchini for this casserole?
While fresh zucchini is ideal for texture, you can use frozen zucchini if you thaw it completely and squeeze out as much water as possible. Frozen zucchini tends to be mushier, so roasting is even more important. Pat it dry thoroughly with paper towels before layering. The casserole will still be delicious, but the texture will be softer. For best results, stick with fresh zucchini.
How do I store and reheat leftovers?
Store leftover casserole in an airtight container in the refrigerator for up to 5 days. For longer storage, freeze individual portions for up to 3 months. To reheat, microwave on high for 2-3 minutes, stirring halfway, or reheat in a 350°F oven for 15-20 minutes until heated through. The cheese may not be as crispy after reheating, but the flavors will meld beautifully. If reheating from frozen, thaw overnight in the fridge first.
Can I make this casserole ahead of time and refrigerate before baking?
Yes, you can assemble the casserole up to 24 hours in advance. Prepare the roasted zucchini and layer everything in the baking dish as instructed. Cover tightly with foil and refrigerate. When ready to bake, remove from the fridge while the oven preheats (about 20 minutes) to take the chill off, then bake as directed, adding 5-10 minutes to the baking time since it starts cold. This is a great time-saver for busy weeknights.
What can I use instead of pepperoni?
You can substitute pepperoni with cooked Italian sausage (crumbled), diced ham, cooked ground beef or turkey, or even shredded rotisserie chicken. For a vegetarian option, use plant-based pepperoni, sliced black olives, or extra mushrooms. Each substitution will change the flavor profile slightly, but all work well with the zucchini and cheese base.
Is this casserole gluten-free?
Yes, this recipe is naturally gluten-free as long as you use a gluten-free marinara sauce and ensure the pepperoni is gluten-free (most brands are, but check labels). The zucchini, cheese, and vegetables contain no gluten. Serve with a side salad or roasted vegetables for a complete gluten-free meal.
Can I add other vegetables?
Absolutely! This casserole is very versatile. Try adding sautéed spinach, chopped kale, roasted red peppers, sun-dried tomatoes, or thinly sliced onions. Just be mindful of moisture—sauté watery vegetables like spinach first and squeeze out excess liquid. You can also add a layer of cooked cauliflower rice for extra volume without many calories.