Every summer, I face the same problem: a garden overflowing with zucchini and a family tired of the same old saute. That is exactly why I perfected this zucchini casserole recipe over the past three years of testing, tweaking, and feeding it to picky eaters.
This is the version my family asks for by name. It is cheesy, golden on top, and never watery, which is the number one complaint I hear from friends who have tried other recipes. I developed a simple moisture-control technique that solves that problem for good.
Whether you need a quick weeknight side dish, a potluck showstopper, or a way to use up five pounds of garden squash, this zucchini casserole recipe delivers. The whole thing comes together in about 45 minutes with ingredients you probably already have. If you love summer squash recipes, this casserole will become a regular in your rotation.
Table of Contents
What You Need: Ingredients for the Best Zucchini Casserole
The beauty of a great zucchini casserole recipe is its simplicity. You do not need fancy ingredients or hard-to-find spices. Here is everything you need for a 9×13 inch baking dish that serves 8 people.
The zucchini: 2 pounds of medium zucchini (about 4 to 5 medium squash). Pick firm, glossy zucchini that feel heavy for their size and have no soft spots.
The binding and flavor base:
2 large eggs (the binder that holds everything together)
1/2 cup heavy cream or whole milk
1 teaspoon Dijon mustard (this is my secret ingredient for depth)
2 cloves garlic, minced
1/2 cup yellow onion, finely diced
1 teaspoon dried oregano
1/2 teaspoon dried thyme
1 teaspoon kosher salt plus extra for drawing out moisture
1/2 teaspoon black pepper
The cheese: 1 cup sharp cheddar cheese, freshly grated, plus 1/2 cup grated Parmesan cheese. Pre-shredded cheese contains anti-caking agents that hurt melting, so always grate your own if possible.
The crunchy topping: 1/2 cup panko breadcrumbs combined with 2 tablespoons melted butter and 2 tablespoons additional Parmesan. You can substitute crushed Ritz crackers if you want a buttery, old-fashioned finish.
One reason I love this zucchini casserole recipe is how forgiving the ingredient list is. You can swap the cheddar for Gruyere, use feta for a tangy Greek twist, or add fresh basil instead of dried herbs. I cover all those variations in detail below.
How to Make Zucchini Casserole (Step by Step)
This is the exact process I use every time. Follow these steps and you will get a casserole with tender zucchini, a creamy interior, and a golden, crunchy top every single time.
Step 1: Prep the zucchini and draw out moisture (15 minutes). Grate the zucchini on the large holes of a box grater, or slice it into thin quarter-inch rounds if you prefer a chunkier texture. Place the grated zucchini in a colander set over a bowl. Sprinkle with 1 teaspoon of kosher salt and toss to combine. Let it sit for 10 to 15 minutes, then use your hands to squeeze out as much liquid as you possibly can. This single step is what separates a perfect casserole from a soup.
Step 2: Preheat and prep the baking dish. Preheat your oven to 375 degrees F. Grease a 9×13 inch baking dish with butter or nonstick spray. If you have time, you can also make a quick low sodium pesto sauce to drizzle on top before serving.
Step 3: Mix the wet ingredients. In a large bowl, whisk together the eggs, heavy cream, Dijon mustard, minced garlic, diced onion, oregano, thyme, salt, and pepper until completely smooth. Fold in the squeezed zucchini, shredded cheddar, and half the Parmesan. Stir until everything is evenly distributed.
Step 4: Transfer to the baking dish. Spread the zucchini mixture into your prepared baking dish in an even layer. Press it down gently with the back of a spoon so the top is flat and the mixture reaches into the corners.
Step 5: Add the crunchy topping. In a small bowl, mix the panko breadcrumbs with the melted butter and remaining Parmesan cheese. Sprinkle this mixture evenly over the entire surface of the casserole.
Step 6: Bake (30 to 35 minutes). Bake uncovered at 375 degrees F for 30 to 35 minutes, until the top is deep golden brown and the edges are bubbling. The center should be set and no longer jiggly when you gently shake the dish.
Step 7: Rest before serving. Let the casserole rest for 10 minutes after taking it out of the oven. This lets the eggs and cheese set up so the casserole slices cleanly instead of falling apart on your serving spoon.
How to Keep Zucchini Casserole from Being Watery
This is the question I get more than any other. Watery zucchini casserole is the most common frustration home cooks face, and it is completely preventable once you understand why it happens.
Zucchini is roughly 95 percent water. When you bake it, that water releases into your casserole and floods the binding ingredients. The result is a soupy, disappointing mess instead of a cohesive, sliceable dish.
Technique 1: Salt and drain. This is the single most important step. Salt draws out moisture through osmosis. Grate or slice your zucchini, salt it generously, wait 15 minutes, and squeeze hard. You will be shocked at how much liquid comes out, often a half cup or more.
Technique 2: Use a cheesecloth or kitchen towel. After the initial squeeze with your hands, wrap the zucchini in a clean kitchen towel or cheesecloth and twist tightly. This removes even more moisture that hand-squeezing alone cannot capture.
Technique 3: Do not skip the binding agents. The eggs and heavy cream in this recipe are not optional. They create the protein structure that absorbs remaining moisture and holds the casserole together. One egg per pound of zucchini is my golden ratio.
Technique 4: Bake uncovered. Covering the dish traps steam and prevents evaporation. Baking uncovered allows excess moisture to escape during the final 15 minutes of cooking. The panko topping also helps by absorbing any moisture that rises to the surface.
Technique 5: Let it rest. Cutting into the casserole immediately releases a flood of trapped steam. A 10-minute rest lets the internal temperature drop slightly and allows the eggs and cheese to reabsorb moisture. Patience here pays off in clean, beautiful slices.
If you follow these five techniques, your casserole will never be watery again. I have tested this recipe with garden zucchini the size of baseball bats, and it still holds together perfectly.
Variations and Substitutions
One of the best things about a zucchini casserole recipe is how adaptable it is. Here are my favorite variations that I have tested extensively, organized by dietary preference and flavor direction.
Keto and Low-Carb Zucchini Casserole
This recipe is already naturally low in carbohydrates. To make it fully keto, replace the panko topping with crushed pork rinds or almond flour mixed with melted butter and Parmesan. Skip the onion and use 1/2 teaspoon of onion powder instead. You can find more ideas in our collection of keto instant pot recipes that pair beautifully with this dish.
Cheese Substitutions
Sharp cheddar is my default, but you have excellent options. Gruyere melts beautifully and adds a nutty, sophisticated flavor. Fontina creates the creamiest, most luxurious texture. Feta adds tang and works well with a Greek herb blend of oregano and mint. A mix of mozzarella and Parmesan gives you that classic Italian-American flavor profile, similar to what you would find in a classic Italian lasagna.
Crunchy Topping Alternatives
Panko gives the lightest, crispiest finish. Crushed Ritz crackers create a buttery, old-fashioned topping that many readers request. Crushed cornflakes add an unexpected savory crunch. For a gluten-free version, use crushed gluten-free crackers or a mix of almond flour and grated Parmesan.
Add-Ins and Upgrades
Layer in thinly sliced tomatoes for an Italian-style casserole. Add browned ground beef or Italian sausage to turn this side dish into a main course. Stir in 1/4 cup of chopped fresh basil and sun-dried tomatoes for a Mediterranean twist. Diced jalapeno and pepper jack cheese give the casserole a southwestern kick.
Dairy-Free Version
Use full-fat coconut milk in place of heavy cream, nutritional yeast instead of Parmesan, and a dairy-free cheese alternative for the cheddar. The texture will be slightly different but still satisfying. Coconut oil works in place of butter for the topping.
Make-Ahead, Storage, and Freezing Instructions
This zucchini casserole recipe is a meal-prep dream once you know the right approach. Here is exactly how to store, freeze, and reheat it for best results.
Can You Make Zucchini Casserole Ahead of Time?
Yes, but with one important caveat. You can assemble the entire casserole up to 24 hours in advance and keep it covered in the refrigerator. However, do not add the breadcrumb topping until right before baking. The topping will get soggy if it sits on the wet mixture overnight. Add the panko mixture right before the casserole goes into the oven.
Refrigerator Storage
Cooked zucchini casserole keeps in an airtight container in the refrigerator for 4 days. The flavor actually improves on day two as the herbs and cheese meld together. I often make a double batch specifically to have leftovers for quick lunches.
Freezing Instructions
You can freeze this casserole either before or after baking, but each method has trade-offs. For best results, I recommend freezing it already baked and cooled.
To freeze baked casserole, let it cool completely to room temperature. Cut into individual portions and wrap each piece tightly in plastic wrap, then aluminum foil. Place the wrapped portions in a freezer bag and freeze for up to 3 months. Individual portions thaw and reheat much better than a whole frozen casserole.
To freeze unbaked casserole, assemble it in a freezer-safe baking dish without the topping. Wrap tightly in plastic wrap and foil, then freeze for up to 2 months. Thaw overnight in the refrigerator, add the topping, and bake at 375 degrees F for 40 to 45 minutes.
Reheating
For refrigerated leftovers, reheat in a 350 degree F oven for 15 minutes or until warmed through. The microwave works in a pinch but makes the topping soft. For frozen portions, thaw overnight in the refrigerator first, then reheat in the oven at 350 degrees F for 20 minutes.
What to Serve with Zucchini Casserole
This casserole works as a side dish or a vegetarian main course depending on how you serve it. Here are my favorite pairings for different occasions.
For a weeknight dinner: Serve alongside grilled chicken, baked salmon, or classic ground beef recipes. The casserole plays a supporting role and adds vegetables to the plate without feeling like a chore.
For a potluck or holiday gathering: Pair with a roasted meat and a fresh green salad. The casserole reheats well and travels in the baking dish, making it ideal for bringing to gatherings.
For a vegetarian meal: Serve with a hearty grain like quinoa or farro, or alongside stuffed squash recipes for a vegetable-forward dinner. Add a side salad with vinaigrette to cut through the richness of the cheese.
For summer barbecues: This casserole is fantastic next to grilled burgers, sausages, or BBQ chicken. It uses up garden zucchini at peak season when the grill is already fired up.
Frequently Asked Questions
What are the 4 ingredients in zucchini casserole?
The four core ingredients in a basic zucchini casserole are fresh zucchini, eggs, cheese, and breadcrumbs. Everything else, including cream, garlic, onion, and herbs, enhances those four fundamentals. This recipe builds on those four with heavy cream, Dijon mustard, and seasonings for maximum flavor.
What are some tips for the best zucchini casserole?
Grate your own cheese for better melting, salt and drain the zucchini for 15 minutes before mixing, never skip the eggs and cream as binding agents, bake uncovered so moisture can escape, and let the casserole rest for 10 minutes before slicing. Always use medium zucchini rather than oversized ones, which are watery and seedy.
How to keep zucchini casserole from being watery?
Salt the grated or sliced zucchini and let it sit for 15 minutes, then squeeze out the liquid using your hands followed by a kitchen towel. Bake uncovered so steam escapes, use eggs and cream as binders, and let the casserole rest for 10 minutes after baking before cutting into it.
What is Jackie Kennedy’s casserole?
Jackie Kennedy’s casserole, sometimes called her zucchini casserole, was a simple baked dish of zucchini, onions, cheese, and breadcrumbs that she reportedly made for family meals. It was a humble, from-scratch recipe reflecting her preference for straightforward, unpretentious home cooking rather than elaborate dishes.
Can you freeze zucchini casserole?
Yes, you can freeze zucchini casserole for up to 3 months. For best results, bake it first, let it cool completely, cut into individual portions, wrap each tightly in plastic wrap and foil, and store in a freezer bag. Thaw overnight in the refrigerator and reheat in a 350 degree F oven for 20 minutes.
How long to bake zucchini casserole and at what temperature?
Bake zucchini casserole uncovered at 375 degrees F for 30 to 35 minutes. The casserole is done when the top is deep golden brown, the edges are bubbling, and the center is set with no jiggle when you gently shake the dish.
Conclusion
This zucchini casserole recipe is the one I turn to all summer long. With a simple salt-and-drain technique, the right ratio of eggs and cream, and a golden panko topping, you get a dish that is creamy, crunchy, and never watery.
Make it once and I guarantee it will become a staple in your kitchen too. Pair it with grilled meats for a weeknight dinner, bring it to your next potluck, or freeze individual portions for easy lunches. When garden season hits and you need more squash ideas, bookmark this page and come back any time.