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Baked Zucchini Casserole placed in a white tray.

Baked Zucchini Casserole

This healthy Baked Zucchini Casserole recipe combines fresh summer zucchini, aromatic garlic, and fresh herbs in a light egg binder, topped with a bubbly, golden layer of melted mozzarella and Parmesan cheese. Made with simple ingredients, this low-carb, gluten-free dish brings authentic Mediterranean flavors to your table. It serves as the perfect family-approved side dish or a light, vegetarian main course that is entirely make-ahead friendly!
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Prep Time 20 minutes
Cook Time 35 minutes
Servings: 6
Course: Side Dish
Cuisine: Mediterranean
Calories: 185
Ingredients Method Notes

Ingredients
  

  • 4 medium zucchini approximately 1.5 lbs, sliced into 1/4-inch rounds
  • 1 tablespoon sea salt used to draw out excess moisture
  • 1.5 tablespoons extra virgin olive oil
  • 1 medium yellow onion finely diced
  • 3 cloves garlic minced
  • 4 large eggs
  • 1/2 cup Parmesan cheese freshly grated
  • 1.5 cups low-moisture mozzarella cheese shredded (divided)
  • 1/4 cup fresh Italian parsley finely chopped
  • 1 teaspoon fresh oregano chopped (or 1/2 teaspoon dried oregano)
  • 1/4 teaspoon freshly cracked black pepper

Method
 

  1. Step 1: Place the sliced zucchini rounds into a colander set over the sink. Sprinkle the sea salt over the zucchini and toss well to coat every piece. Let it stand for 15 to 20 minutes to draw out the water. Wrap the zucchini in a clean kitchen tea towel and squeeze firmly to extract as much excess liquid as humanly possible.
  2. Step 2: Heat the extra virgin olive oil in a skillet over medium heat. Add the finely diced yellow onion and sauté for 4 to 5 minutes until soft and translucent. Stir in the minced garlic and cook for an additional 1 minute until fragrant. Remove the skillet from the heat and allow the mixture to cool slightly.
  3. Step 3: In a large mixing bowl, vigorously whisk the 4 large eggs. Stir in the grated Parmesan cheese, 1 cup of the shredded mozzarella cheese, chopped fresh parsley, oregano, black pepper, and the cooled onion and garlic mixture.
  4. Step 4: Gently fold the thoroughly drained zucchini rounds into the egg and cheese mixture until every slice is completely and evenly coated.
  5. Step 5: Lightly grease a 9x13-inch baking dish with a touch of olive oil. Pour the zucchini mixture into the dish, smoothing it out into an even layer. Top the entire surface evenly with the remaining 1/2 cup of shredded mozzarella cheese.
  6. Step 6: Bake uncovered in a preheated oven at 375°F (190°C) for 30 to 35 minutes. It is done when the center is fully set, the edges are bubbly, and the top cheese layer has transformed into a beautiful, golden-brown crust.

Notes

  • The Squeeze Test: Zucchini is over 90% water. Do not skip salting and wringing it out in a towel, or your casserole will turn into a watery soup.
  • Grate Your Own: Avoid pre-shredded bagged cheese. It contains anti-caking starches that prevent it from melting into a perfectly smooth, gooey crust.
  • Bake Uncovered: Leaving the dish uncovered lets steam escape during baking, ensuring a firm texture and a beautifully crisp, golden top.
  • Let It Rest: Give the casserole 5 to 10 minutes to settle on the counter after baking. This lets the egg custard set completely so you can cut clean, beautiful squares.
  • Make-Ahead Strategy: You can salt, drain, and dry the zucchini a day in advance. Store the dried zucchini and the whisked egg mixture in separate airtight containers in the fridge, then combine and bake right before serving.