Summer Zucchini Onion Pie

On the first hot weekend of summer I made this zucchini onion pie because my garden was overflowing and I wanted something that felt like a light main dish and a side all at once. The zucchini onion pie came out with a golden, slightly crisp crust and a creamy interior that held its shape when sliced—no watery puddles—thanks to a few careful steps I learned the hard way. If you want an easy, dependable summer recipe that uses fresh zucchini and pantry basics, keep reading.

Why this zucchini onion pie works

This zucchini onion pie is built around two simple but crucial techniques: sweating excess moisture from the zucchini and onion, and using a firm custard ratio so the filling sets without becoming rubbery. Zucchini is mostly water, and the common problem with summer vegetable pies is a soggy crust or a filling that separates. During testing I sliced the zucchini thin, salted it, and pressed out the juice; then I sautéed the onion briefly to concentrate its sweetness. I also lightly blind-baked the crust edge for 6 minutes to help keep the bottom crisp. What changed between the first attempt and the final version was the addition of a small amount of cornstarch to the custard and a quick drain of the vegetable juices—those two adjustments fixed the runny filling I had on attempt one.

Key takeaways

• Salt and press thinly sliced zucchini to remove excess water before mixing it into the filling.
• Partially bake the crust and toast the bottom slightly to prevent sogginess.
• Use a custard ratio of eggs to cream (3 eggs to 1 cup cream for a 9-inch pie) and a tablespoon of cornstarch for firm, sliceable results.
• Sauté the onions briefly to concentrate flavor and reduce moisture.

Ingredients you’ll need and what to substitute

The backbone of the dish is zucchini, onion, eggs, and a mixed dairy custard. I use 2 medium zucchini for a 9-inch pie so the slices layer nicely without overcrowding. For richness I prefer half-and-half or whole milk with a splash of heavy cream; if you want a lighter pie, use a full cup of whole milk plus 2 tablespoons of melted butter for richness. The cheese I choose is a mix of sharp cheddar and grated Parmesan for flavor and structure—cheddar melts and gives creaminess, while Parmesan adds savory depth. If you can’t find cheddar, Gruyère, Monterey Jack, or a firm Swiss work well but will slightly change the flavor.

Two substitutions worth noting: if you prefer a herb-forward pie, swap 1 teaspoon of dried thyme for 1 tablespoon of chopped fresh basil (add basil after cooling). For a gluten-free crust, use a 9-inch store-bought gluten-free pie shell or a simple almond-flour crust, but expect a slightly different texture and shorter bake time—watch the edges closely.

Equipment

You’ll need a 9-inch pie dish (glass or metal), a sharp chef’s knife or mandoline for thin zucchini slices, a skillet for softening the onion, and a mixing bowl for the custard. A baking sheet to place the pie on helps avoid spills in the oven. If you don’t have a pie dish, a 9-inch tart pan with a removable bottom works; if using a tart pan, blind-bake the crust for the same time but keep an eye on the edges.

How to make zucchini onion pie

Prepare the crust and vegetables

Start by preheating your oven to 375°F. Roll out or press a 9-inch refrigerated pie crust into a 9-inch pie dish and crimp the edges. Prick the bottom a few times with a fork, line with parchment and pie weights or dried beans, and blind-bake for 12 minutes; remove the weights and bake another 4 minutes until the crust looks set and just starting to color. While the crust is warming, thinly slice 2 medium zucchini on a mandoline or with a knife to about 1/8-inch thickness and place them in a bowl. Salt the zucchini lightly (about 1 teaspoon kosher salt), toss, and let sit for 10 minutes to draw out water. After 10 minutes, press handfuls of zucchini in a clean kitchen towel or between paper towels to extract as much liquid as possible—this step is critical for avoiding a watery pie.

Sauté the onion and assemble the filling

Slice 1 large yellow onion thinly and heat 1 tablespoon olive oil in a skillet over medium heat. Add the onion and a pinch of salt and cook, stirring occasionally, until softened and translucent, about 7–8 minutes. You don’t need caramelization here—just softened, sweeter onion and reduced moisture. Let the onion cool slightly, then combine in a bowl with the drained zucchini, 1 cup shredded sharp cheddar, 1/2 cup grated Parmesan, and 1 tablespoon chopped fresh parsley (optional).

Make the custard and bake

In a separate bowl whisk together 3 large eggs, 1 cup half-and-half (or 3/4 cup whole milk + 1/4 cup heavy cream), 1 tablespoon cornstarch, 1/2 teaspoon black pepper, and 1/2 teaspoon dried thyme (or 1 teaspoon fresh thyme). The cornstarch helps the filling set without becoming rubbery; it also absorbs residual vegetable moisture. Fold the egg mixture into the zucchini-onion-cheese mix until evenly distributed. Spoon the filling into the pre-baked pie shell and smooth the top. Place the pie on a rimmed baking sheet and bake at 375°F for 35–40 minutes, until the center is set and the top is lightly golden. The center should jiggle slightly but not be liquid; it will firm as it cools.

Rest and serve

Allow the pie to cool for 15–20 minutes before slicing; this resting time makes for cleaner slices. The finished pie will have a glossy, lightly browned top with visible flecks of zucchini and onion and a crisp edge where the crust browned. Serve warm or at room temperature with a simple green salad.

Things I learned the hard way

• If you skip salting and pressing the zucchini, the pie leaked liquid and the crust went soggy—always salt and squeeze.
• Using only milk produced a looser filling that needed extra baking time; the half-and-half or milk/cream mix gives a silkier mouthfeel while setting reliably.
• I once overcooked the onions until brown; the pie tasted slightly bitter. Keep the onions just softened and translucent for sweetness.
• Blind-baking the crust by at least 12 minutes (with weights) then removing weights for a short finish prevents a raw bottom and reduces sogginess.
• Don’t overload the pie with too many vegetables; a thinner, even layer bakes more consistently and firms better.

Variations to try

• Herb-forward: add 2 tablespoons chopped fresh basil and omit dried thyme; bake the same amount. Add basil after the pie rests to keep it bright.
• Tomato & zucchini pie: layer 1 medium ripe tomato (salted and patted dry) on top of the zucchini mixture and reduce cheddar to 3/4 cup; bake the same time but expect slightly more moisture—press tomato slices before using.
• Crustless version: skip the crust and bake the filling in a well-greased 9-inch pie plate at 350°F for 30-35 minutes; reduce total time and expect a denser texture.
• Cheesy swap: use 1 cup grated Gruyère for a nuttier flavor; no time adjustment needed.

Storage, freezing, and reheating

Refrigerate leftover slices in an airtight container for up to 3 days. To reheat, place slices on a baking sheet and warm at 325°F for 10–12 minutes until heated through—this helps restore some of the crust’s crispness. The pie freezes best as whole baked rounds wrapped tightly in plastic and foil; freeze up to 2 months. Thaw overnight in the refrigerator, then reheat at 325°F for 20–25 minutes. Note: freezing can slightly change the texture of the zucchini, making it softer; for best texture eat within the first week.

What to serve with zucchini onion pie

Try serving this pie with a crisp green salad tossed in lemon vinaigrette, a bowl of chilled tomato gazpacho on hot days, or a simple grain salad like farro with herbs for a more substantial meal. For potlucks, cut into wedges and pair with pickled vegetables or a zesty cucumber salad to balance the richness.

Summer Zucchini Onion Pie

A sliceable savory pie of thin zucchini and sweet onion in a creamy, lightly set custard with a crisp blind-baked crust—perfect for summer lunches or potlucks.

Print Recipe Pin Recipe

Prep Time 25 minutes mins

Cook Time 40 minutes mins

Total Time 1 hour hr 5 minutes mins

Servings: 6 servings

Calories: 360

Ingredients Equipment Method Notes

Ingredients

  

• 1 prepared 9-inch pie crust homemade or refrigerated, chilled
• 2 medium zucchini about 1 1/2 pounds, thinly sliced (about 1/8-inch)
• 1 large yellow onion thinly sliced
• 1 teaspoon kosher salt divided
• 1 tablespoon olive oil
• 3 large eggs
• 1 cup half-and-half or 3/4 cup whole milk + 1/4 cup heavy cream
• 1 tablespoon cornstarch
• 1 cup shredded sharp cheddar cheese
• 1/2 cup grated Parmesan cheese
• 1/2 teaspoon black pepper
• 1/2 teaspoon dried thyme or 1 teaspoon fresh, optional
• 1 tablespoon chopped fresh parsley optional

Optional garnish

• Fresh basil leaves for serving optional

Equipment

• 1 9-inch pie dish
• 1 Mandoline or sharp chef's knife
• 1 10-inch skillet
• 1 rimmed baking sheet

Method

 

Prep and blind-bake crust

1. Preheat the oven to 375°F and place the pie crust in a 9-inch pie dish; prick the bottom with a fork, line with parchment and pie weights, and blind-bake for 12 minutes. Remove weights and bake another 4 minutes until just starting to color.

Prepare vegetables

1. Thinly slice zucchini to about 1/8-inch thickness, place in a bowl, sprinkle with 3/4 teaspoon kosher salt, toss, and let sit 10 minutes. After resting, press the zucchini in a clean towel to remove excess moisture.
2. Slice the onion thinly and heat 1 tablespoon olive oil in a skillet over medium heat; add the onion with a pinch of salt and cook 7–8 minutes until softened and translucent, then cool slightly.

Make filling

1. In a bowl whisk together 3 eggs, 1 cup half-and-half, 1 tablespoon cornstarch, 1/2 teaspoon black pepper, and 1/2 teaspoon dried thyme. Combine the drained zucchini, cooked onion, 1 cup cheddar, 1/2 cup Parmesan, and 1 tablespoon parsley (if using) in a mixing bowl, then fold in the egg mixture until evenly combined.

Bake pie

1. Spoon the filling into the partially baked pie shell and smooth the top. Place the pie on a rimmed baking sheet and bake at 375°F for 35–40 minutes, until the top is lightly golden and the center jiggles only slightly.

Rest and serve

1. Cool the pie on a rack for 15–20 minutes before slicing; garnish with fresh basil if desired and serve warm or at room temperature.

Notes

Pressing and draining zucchini is essential to avoid a watery pie; add the cornstarch to the custard for a firmer set. You can swap cheddar for Gruyère or Monterey Jack; for a crustless version bake at 350°F for 30–35 minutes and expect a denser texture. Store leftovers refrigerated up to 3 days and reheat at 325°F to crisp the crust.

Frequently asked questions

Can I use frozen zucchini? Yes, but thaw and press out all excess water before using; frozen zucchini releases more liquid so extra pressing and an extra tablespoon of cornstarch help.

Do I have to blind-bake the crust? Blind-baking is highly recommended to prevent a soggy bottom, especially with high-moisture fillings like zucchini; if you skip it, bake the pie on a lower rack and expect a softer crust.

How do I know the pie is done? The pie is done when the top is lightly golden and the center jiggles only slightly; a toothpick inserted near the center should come out with a few moist crumbs, not wet custard.

Can I make this ahead? Yes—bake the pie, cool completely, then refrigerate up to 24 hours. Reheat at 325°F for about 15 minutes before serving to refresh the crust.

Can I double the recipe? Yes, double ingredients and bake in two 9-inch pie plates or one deep-dish 10-inch—bake time may increase by 5–10 minutes depending on depth, so watch for the same doneness cues.

Closing

This zucchini onion pie takes summer zucchini and turns it into a dependable sliceable savory pie with a crisp edge and creamy interior—one I’m happy to make again when the garden is generous.