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Cheesy garlic zucchini casserole with tender zucchini, melted mozzarella, Parmesan, and a golden breadcrumb topping.

Cheesy Garlic Zucchini Casserole

Tender zucchini layered with garlic, creamy cheese, mozzarella, Parmesan, and a crispy buttery breadcrumb topping.
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Prep Time 25 minutes
Cook Time 40 minutes
Total Time 1 hour 35 minutes
Course: Dinner
Cuisine: American
Ingredients Method Notes

Ingredients
  

  • 4 medium zucchini about 2 pounds total, sliced into 1/4-inch rounds
  • 1 teaspoon salt divided, plus more to taste
  • 1 tablespoon olive oil
  • 1 small yellow onion finely diced
  • 4 garlic cloves minced
  • 4 ounces cream cheese softened
  • 1/2 cup sour cream
  • 1 large egg
  • 1 1/2 cups shredded low-moisture mozzarella cheese
  • 1/2 cup freshly grated Parmesan cheese divided
  • 1 teaspoon Italian seasoning
  • 1/2 teaspoon freshly ground black pepper
  • 3/4 cup panko breadcrumbs
  • 2 tablespoons unsalted butter melted
  • 2 tablespoons chopped fresh parsley

Method
 

  1. Wash and dry the zucchini. Trim the ends and slice into approximately 1/4-inch rounds.
  2. Spread the zucchini slices across clean kitchen towels or a large tray and sprinkle lightly with salt.
  3. Let the zucchini rest for 20 minutes.
  4. Pat the slices thoroughly dry to remove the moisture released by the salt.
  5. Preheat the oven to 375°F (190°C). Lightly grease a 9 x 13-inch baking dish.
  6. Heat the olive oil in a skillet over medium heat.
  7. Add the diced onion and cook for 4–5 minutes, stirring occasionally, until softened.
  8. Add the minced garlic and cook for 30–60 seconds, just until fragrant.
  9. In a medium bowl, stir together the softened cream cheese and sour cream until smooth.
  10. Beat in the egg.
  11. Stir in the Italian seasoning, black pepper, and half of the grated Parmesan.
  12. Fold the sautéed onion and garlic into the cheese mixture.
  13. Arrange half of the zucchini slices in the prepared baking dish, overlapping them slightly.
  14. Spoon half of the creamy garlic mixture over the zucchini.
  15. Sprinkle half of the mozzarella over the top.
  16. Repeat with the remaining zucchini, creamy mixture, and mozzarella.
  17. In a small bowl, combine the panko breadcrumbs, melted butter, and remaining Parmesan.
  18. Scatter the breadcrumb mixture loosely across the top of the casserole.
  19. Cover loosely with aluminum foil and bake for 20 minutes.
  20. Remove the foil and continue baking for 15–20 minutes, until the zucchini is tender, the cheese is bubbling, and the topping is golden.
  21. If desired, broil for 1–2 minutes for additional browning, watching carefully.
  22. Remove from the oven and rest for 10 minutes.
  23. Garnish with chopped fresh parsley and serve warm.

Notes

Salting the zucchini before baking helps prevent a watery casserole.
After salting, pat the zucchini thoroughly dry before layering it in the baking dish.
Use low-moisture mozzarella rather than fresh mozzarella for the best texture.
Keep the zucchini slices around 1/4 inch thick so they become tender without turning mushy.
Do not overcook the garlic when sautéing.
Scatter the breadcrumb topping loosely rather than pressing it into the cheese.
Allow the casserole to rest for 10 minutes after baking before serving.
Store leftovers in the refrigerator for up to 4 days.
The casserole can be frozen for up to 1 month, although the zucchini will become softer after thawing.