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–+ servings

Caramelized Onion and Zucchini Quiche

This Caramelized Onion and Zucchini Quiche combines sweet caramelized onions, fresh zucchini, creamy mozzarella, Parmesan cheese, and a rich egg custard baked inside a flaky pie crust. Perfect for brunch, meal prep, holidays, or an easy summer dinner, it's a versatile recipe you'll make again and again.
3 from 1 vote
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Course: Breakfast, Brunch, dinner, lunch, meal prep
Cuisine: French
Keyword: easy quiche recipe, homemade zucchini quiche, onion and zucchini quiche, seasonal zucchini quiche recipe, summer quiche recipe, zucchini and mozzarella quiche
Prep Time: 30 minutes
Cook Time: 50 minutes
Total Time: 1 hour 20 minutes
Servings: 8 slices

Ingredients 

Filling

  • 2 large eggs
  • 4 large egg yolks
  • 1 cup heavy cream
  • 2 medium zucchini shredded and squeezed very dry (about 2 cups after draining)
  • 1 large sweet onion thinly sliced
  • 1 tablespoon unsalted butter, or olive oil
  • 8 ounces fresh mozzarella shredded or torn into pieces
  • ½ cup freshly grated Parmesan cheese
  • 1 teaspoon garlic powder
  • 1 teaspoon dried parsley
  • 1 teaspoon kosher salt
  • ½ teaspoon freshly cracked black pepper

Optional Garnish

  • Fresh basil
  • Additional grated Parmesan

Instructions

  • Preheat the oven to 425°F.
  • Place the pie crust into a 9-inch pie dish. Crimp the edges and dock the bottom with a fork. Set aside
  • Heat the butter in a skillet over medium-low heat. Add the onions with a pinch of salt and cook for 30–40 minutes, stirring occasionally, until deeply golden and caramelized. Let cool slightly.
  • Shred the zucchini and squeeze out as much moisture as possible using a clean kitchen towel.
  • In a large bowl, whisk together the eggs, egg yolks, heavy cream, garlic powder, parsley, salt, and pepper.
  • Fold in the zucchini, caramelized onions, mozzarella, and Parmesan.
  • Pour the filling into the prepared crust.
  • Bake at 425°F for 20 minutes, then reduce the oven temperature to 350°F and bake another 30 minutes, or until the center is just set.
  • If the crust browns too quickly, loosely cover the edges with foil.
  • Let the quiche cool for 10–15 minutes before slicing.
  • Garnish with fresh basil and additional Parmesan, if desired.

Notes

  • Drain the zucchini well. Place the shredded zucchini in a towel-lined colander, sprinkle lightly with salt, and let it rest for 10 minutes before squeezing out as much liquid as possible.
  • Caramelize the onions low and slow. Taking the time to caramelize the onions develops a rich, sweet flavor that makes this quiche extra special.
  • If you want a crispier crust, blind bake it first. This helps keep the bottom crust crisp and flaky, even with the moisture from the zucchini.
  • Let the quiche rest before slicing. Cooling for 10–15 minutes allows the custard to fully set for clean, beautiful slices.