This zucchini and squash casserole recipe is the one I reach for the second my garden (or the farmers market table) starts overflowing with summer vegetables. It layers tender zucchini and yellow squash with a creamy cheese sauce and a buttery cracker topping, then bakes until golden and bubbling.
It’s the kind of side dish that shows up at potlucks, Sunday dinners, and weeknight tables alike, and it disappears just as fast at all three. Below you’ll find the classic version, the one most home cooks grew up eating, along with tips, swaps, and everything else you need to make it right the first time.
| Quick Recipe Summary | |
|---|---|
| Prep Time | 20 minutes |
| Cook Time | 35 minutes |
| Total Time | 55 minutes |
| Servings | 8 servings |
| Difficulty Level | Easy |
If you’d rather skip the zucchini altogether, my squash casserole uses the same method with just yellow squash.
Why You’ll Love This Zucchini and Squash Casserole Recipe
This isn’t a fussy recipe, and it doesn’t pretend to be. It’s cheesy, a little crunchy on top, and built from vegetables you can find at any grocery store in July.
It also happens to solve the “too much squash” problem better than almost anything else I make.
- Uses up garden overflow. If you grow zucchini, you know the feeling of having ten more than you planned for. This recipe eats through several at once.
- Feeds a crowd. One 9×13 dish covers eight side-dish servings, which makes it a solid pick for potlucks and holiday tables.
- Make-ahead friendly. You can assemble it the night before and bake it the next day.
- Balanced texture. Tender squash, a creamy middle layer, and a crisp cracker top, all in one bite.
- Kid-approved. The cheese and buttery topping win over even the pickiest vegetable skeptics at my table.
- Naturally gluten-free adaptable. Swap the crackers for a gluten-free version and the rest of the recipe stays the same.
You might also enjoy: Sweet Potato Casserole
Ingredients
Here’s everything you need for one full 9×13-inch casserole. Exact measurements are in the recipe card below, but here’s the full list with both imperial and metric amounts.
- Zucchini: 2 pounds (900g), sliced into ¼-inch rounds
- Yellow summer squash: 1.5 pounds (680g), sliced into ¼-inch rounds
- Yellow onion: 1 medium, diced
- Unsalted butter: 3 tablespoons (42g), for sautéing
- Kosher salt: 1 teaspoon, plus more for sweating the squash
- Black pepper: ½ teaspoon
- Garlic powder: ½ teaspoon
- Large eggs: 2, beaten
- Sour cream: 1 cup (240g)
- Sharp cheddar cheese: 2 cups (225g), shredded and divided
- Parmesan cheese: ½ cup (50g), grated
- Ritz crackers: 1 sleeve (about 35 crackers), crushed
- Butter, melted: ¼ cup (60g), for the topping
- Fresh parsley: 2 tablespoons, chopped, for garnish (optional)
If you’re stocking up for a holiday spread, I usually make this alongside my green bean casserole for extra color on the table.
Kitchen Equipment Needed
You don’t need anything fancy here, just a few basics that make slicing and assembling go faster.
- Sharp chef’s knife or mandoline slicer: For even ¼-inch squash rounds
- Large skillet: For sautéing the onion and squash
- Colander: For draining the salted squash
- Mixing bowls: A large one for the cheese mixture, a small one for the topping
- 9×13-inch baking dish: Glass or ceramic both work fine
- Box grater: If you’re shredding your own cheddar instead of buying pre-shredded
- Measuring cups and spoons
- Rubber spatula
- Aluminum foil
Read Also: Hashbrown Casserole
Recommended Products for This Recipe
These are products I’ve genuinely used while making this casserole more times than I can count. None of them are required, but each one solves a specific annoyance I ran into early on.
1. OXO Good Grips Mandoline Slicer
Uneven squash slices were my biggest problem when I first started making this dish. Thick pieces stayed crunchy while thin ones turned to mush, and a mandoline fixed that overnight. It also cuts the prep time roughly in half compared to a knife.
2. Ceramic 9×13 Baking Dish
A ceramic dish heats more evenly than thin metal pans, which matters a lot here since uneven heat means soggy spots. I also like that it goes straight from the oven to the table without looking like a sheet pan.
3. Salad Spinner
This sounds unnecessary until you try it. After salting and rinsing the squash, a salad spinner pulls out way more moisture than paper towels alone, and that’s the single biggest factor in whether your casserole turns out watery.
4. Cabot Vermont Sharp Cheddar Cheese
I switched to a real block of sharp cheddar instead of the pre-shredded bags years ago, and the difference in how it melts is noticeable. Pre-shredded cheese has anti-caking starch on it that keeps the sauce from going fully smooth.
5. Glass Mixing Bowl Set
Nothing groundbreaking, just a sturdy set that doesn’t stain or hold onion smell the way plastic bowls do. I use the largest one for the cheese mixture and the smallest for the cracker topping every single time.
For another cheesy side worth trying: Cheesy Potatoes
Step-by-Step Instructions: How to Make Zucchini and Squash Casserole
Follow these simple steps and you’ll have a golden, bubbling zucchini and squash casserole ready in under an hour.
1. Slice and Salt the Squash
- Slice the zucchini and yellow squash into even ¼-inch rounds, using a mandoline if you have one.
- Spread the slices out in a single layer on a baking sheet or in a colander set over the sink.
- Sprinkle generously with kosher salt and let them sit for 15 to 20 minutes.
- Pat the slices dry with paper towels or a clean kitchen towel. This step pulls out excess water so your casserole doesn’t turn watery in the oven.
2. Sauté the Onion and Squash
- Preheat your oven to 350°F (175°C) and lightly grease the 9×13 baking dish.
- Melt 3 tablespoons of butter in a large skillet over medium heat.
- Add the diced onion and cook for 4 to 5 minutes, stirring occasionally, until softened and translucent.
- Add the dried zucchini and squash slices to the skillet in batches if needed.
- Cook for 4 to 6 minutes, stirring gently, until just crisp-tender. You want a little bite left, since the squash will keep cooking in the oven.
- Season with the salt, pepper, and garlic powder, then remove from heat.
3. Make the Creamy Cheese Mixture
- In a large mixing bowl, whisk together the beaten eggs and sour cream until smooth.
- Fold in 1½ cups of the shredded cheddar cheese, reserving the remaining ½ cup for topping later.
- Add the grated Parmesan cheese and stir to combine.
- Gently fold the sautéed zucchini, squash, and onion into the egg and cheese mixture until every slice is coated.
4. Assemble the Casserole
- Pour the squash and cheese mixture into the prepared baking dish.
- Spread it into an even layer with a rubber spatula, making sure there are no large gaps or air pockets.
- Sprinkle the reserved ½ cup of cheddar cheese evenly over the top.
5. Make the Cracker Topping
- In a small bowl, combine the crushed Ritz crackers with the ¼ cup melted butter.
- Stir until every crumb is coated and the mixture looks like wet sand.
- Sprinkle the buttered cracker crumbs evenly over the cheese layer.
6. Bake
- Bake uncovered for 30 to 35 minutes, until the topping is golden brown and the edges are bubbling.
- If the top browns too quickly before the center is hot, tent it loosely with aluminum foil for the last 10 minutes.
7. Rest and Serve
- Let the casserole rest for 10 minutes before serving. This gives the sauce time to set so it doesn’t run all over the plate.
- Garnish with chopped fresh parsley if you’d like, then serve warm.
I learned a lot of this layering technique from making my funeral potatoes, which uses a similar buttery crumb topping.
Tips for The Best Zucchini and Squash Casserole
A few things I learned the hard way, mostly by skipping steps I shouldn’t have.
- Don’t skip the salting step. I tried rushing this once and ended up with a soupy casserole that never set properly.
- Slice evenly. Uneven slices cook at different rates, so thick pieces stay raw while thin ones disintegrate.
- Use full-fat sour cream. Light or fat-free versions tend to separate when baked and make the sauce watery.
- Shred your own cheese when you can. It melts smoother than the pre-shredded bags, which are coated in anti-caking starch.
- Let it rest before slicing. Cutting into it too soon means a runny mess instead of clean squares.
- Check at the 25-minute mark. Ovens vary, and the topping can go from golden to burnt fast in the last few minutes.
- Drain twice if your squash is very watery. Some squash varieties hold onto more moisture, so a second pat-dry round never hurts.
You might also enjoy: Au Gratin Potatoes
What to Serve with Zucchini and Squash Casserole
This casserole plays the supporting role well, which means it pairs with almost anything coming off the grill or out of the oven. I usually build the rest of the meal around whatever protein I have on hand.
- Grilled or roasted meats: Roast chicken, grilled lemon herb chicken, or smoked beef tenderloin all work well alongside it.
- Holiday mains: It holds its own next to a baked ham or a Thanksgiving turkey on a holiday table.
- Lighter seafood: Baked salmon with asparagus balances out the richness of the cheese.
- Bread: A loaf of crusty bread or warm dinner rolls is great for soaking up any extra sauce.
- Simple salads: A crisp green salad or a coleslaw adds crunch and a little acidity to cut through the richness.
- Potlucks and cookouts: It travels well in its baking dish, making it an easy contribution to summer cookouts.
If you want another creamy side to round out the meal, my scalloped potatoes pair well with most of the same mains.
Variations of Zucchini and Squash Casserole
I’ve played around with this recipe more times than I can count, mostly because I always seem to have something in the fridge that needs using up.
- Mexican-style: Swap the cheddar for pepper jack and add a can of diced green chiles.
- Italian-style: Use mozzarella and Parmesan, stir in chopped fresh basil, and swap the Ritz topping for seasoned panko breadcrumbs.
- Bacon version: Fold in a half cup of cooked, crumbled bacon for a smokier flavor.
- Lighter version: Use Greek yogurt instead of sour cream and skip the buttered topping in favor of a light dusting of Parmesan.
- Gruyere swap: Replace the cheddar with shredded Gruyere for a nuttier, more grown-up flavor.
- Vegetable boost: Add a cup of frozen corn or diced bell pepper along with the squash for more color and texture.
- Spicy kick: Stir in a pinch of red pepper flakes or a few dashes of hot sauce into the egg mixture.
Read Also: Stuffed Acorn Squash
Storage and Reheating
This casserole keeps well, which makes it a solid choice for meal prep or holiday leftovers.
- Refrigerator: Store covered tightly in the baking dish or transferred to an airtight container for up to 4 days.
- Freezer: Freeze the baked and cooled casserole for up to 2 months, though the texture softens slightly after thawing.
- Reheating in the oven: Cover with foil and reheat at 350°F (175°C) for 15 to 20 minutes, until warmed through.
- Reheating in the microwave: Heat individual portions in 60-second bursts until hot, though the topping won’t stay crisp.
- Make-ahead tip: Assemble the casserole up to the baking step, cover, and refrigerate for up to 24 hours. Add the cracker topping right before baking so it stays crunchy.
- Avoid freezing with the topping on. If you plan to freeze it, hold off on adding the cracker topping until you’re ready to bake.
For a soup that uses similar squash-prep tricks, try: Roasted Butternut Squash Soup
Nutritional Facts
Approximate values per serving, based on 8 servings.
| Nutrition (Per Serving) | |
|---|---|
| Calories | 285 kcal |
| Carbohydrates | 13g |
| Protein | 11g |
| Fat | 22g |
| Saturated Fat | 12g |
| Cholesterol | 90mg |
| Sodium | 410mg |
| Fiber | 2g |
| Sugar | 5g |
When I want a sweeter contrast on the plate, I’ll add a batch of my maple glazed carrots next to this casserole.
Health Benefits of Key Ingredients
Beyond tasting good, the vegetables in this casserole are doing some real work nutritionally.
- Zucchini: Low in calories and a good source of potassium, vitamin C, and antioxidants like lutein.
- Yellow squash: Provides vitamin A, B6, magnesium, and fiber, all in a vegetable that’s mostly water by weight.
- Onion: Contains quercetin, a plant compound linked to anti-inflammatory effects.
- Eggs: A complete protein source that also helps bind the casserole together.
- Cheddar and Parmesan cheese: Provide calcium and protein, though they’re best enjoyed in moderation given the saturated fat content.
- Garlic powder: Offers small amounts of the same beneficial compounds found in fresh garlic, including allicin precursors.
For another vegetable-forward side, try: Roasted Brussels Sprouts with Bacon
FAQs About Zucchini and Squash Casserole
1. Can I use only zucchini or only yellow squash?
Yes, you can use either vegetable on its own if that’s what you have on hand.
The texture and flavor will be nearly identical, you’ll just lose a bit of the color contrast.
2. Why is my casserole watery?
This almost always comes down to skipping or rushing the salting step.
Salt the squash, let it sit for 15 to 20 minutes, then pat it thoroughly dry before cooking.
3. Can I make this casserole ahead of time?
Yes, assemble everything except the cracker topping and refrigerate it for up to 24 hours.
Add the topping right before baking so it bakes up crisp instead of soggy.
4. What can I use instead of Ritz crackers?
Panko breadcrumbs, crushed saltines, or crushed cornflakes all work as a substitute.
Mix whichever you choose with melted butter the same way for that golden, crunchy finish.
5. Can I make this casserole gluten-free?
Yes, swap the Ritz crackers for a gluten-free cracker or gluten-free panko.
Everything else in the recipe is naturally gluten-free as written.
My creamed spinach is another vegetable side I make on repeat for the exact same reasons.
Zucchini and Squash Casserole
Ingredients
- 2 pounds zucchini - 900g, sliced into ¼-inch rounds
- 1.5 pounds yellow summer squash - 680g, sliced into ¼-inch rounds
- 1 yellow onion - medium, diced
- 3 tablespoons unsalted butter - 42g, for sautéing
- 1 teaspoon kosher salt - plus more for sweating the squash
- 0.5 teaspoon black pepper
- 0.5 teaspoon garlic powder
- 2 large eggs - beaten
- 1 cup sour cream - 240g, full-fat recommended
- 2 cups sharp cheddar cheese - 225g, shredded and divided (1½ cups for mixture, ½ cup for topping)
- 0.5 cup Parmesan cheese - 50g, grated
- 1 sleeve Ritz crackers - about 35 crackers, crushed
- 0.25 cup butter - 60g, melted, for the topping
- 2 tablespoons fresh parsley - chopped, for garnish (optional)
Equipment
- Sharp chef’s knife
- Mandoline slicer - optional
- Large skillet
- Colander
- Mixing bowls - large one for cheese mixture, small one for topping
- 9×13 inch baking dish - glass or ceramic
- Box grater - if shredding your own cheese
- Measuring cups and spoons
- Rubber spatula
- Aluminum foil - for tenting if needed
- Salad spinner - optional but recommended
Method
- Slice zucchini and yellow squash into even ¼-inch rounds. Spread on a baking sheet or in a colander, sprinkle generously with salt, and let sit for 15-20 minutes. Pat dry thoroughly with paper towels or a clean kitchen towel.
- Preheat oven to 350°F (175°C) and grease a 9×13 baking dish. Melt 3 tablespoons butter in a large skillet over medium heat. Add diced onion and cook 4-5 minutes until translucent. Add squash slices and cook 4-6 minutes until crisp-tender. Season with salt, pepper, and garlic powder, then remove from heat.
- In a large bowl, whisk eggs and sour cream until smooth. Fold in 1½ cups of the cheddar cheese and the Parmesan cheese. Gently fold in the sautéed vegetables until well coated.
- Pour the squash mixture into the prepared baking dish and spread evenly. Sprinkle the reserved ½ cup of cheddar cheese over the top.
- In a small bowl, combine crushed Ritz crackers with ¼ cup melted butter until all crumbs are coated. Sprinkle evenly over the cheese layer.
- Bake uncovered for 30-35 minutes until golden brown and bubbling. Tent with foil if the top browns too quickly. Rest for 10 minutes before serving.
Nutrition
Notes
- Don’t skip salting: This step removes excess moisture and prevents a watery casserole. Squeeze or pat the squash very dry after salting.
- Slice evenly: Use a mandoline for uniform ¼-inch slices so all pieces cook at the same rate.
- Use full-fat sour cream: Light versions tend to separate and create a watery sauce when baked.
- Shred your own cheese: Pre-shredded cheddar contains anti-caking starch that prevents smooth melting.
- Make ahead: Assemble without the cracker topping up to 24 hours ahead, refrigerate, then add topping just before baking.
- Gluten-free option: Substitute the Ritz crackers with gluten-free crackers or gluten-free panko breadcrumbs.
- Variations: Try Mexican-style with pepper jack and green chiles, or Italian-style with mozzarella, basil, and panko.
- Storage: Refrigerate leftovers in an airtight container for up to 4 days. Reheat covered at 350°F for 15-20 minutes.
Private Notes
Tried this recipe?
Let us know how it was!Final Thoughts
This zucchini and squash casserole is the dish I keep coming back to every summer, mostly because it’s hard to mess up once you know the salting trick.
It’s cheesy, comforting, and an easy way to make peace with an overflowing vegetable basket.
Give it a try the next time your fridge is full of squash, and let me know in the comments how yours turned out. I’d love to hear what variations you tried.
Recommended:
- Mashed Potatoes
- Twice Baked Potatoes
- Broccoli Salad
- Coleslaw
- Baked Ham
- Honey Baked Ham
- Roast Chicken
- Prime Rib
- Air Fryer Zucchini Parmesan Chips
- Grilled Lemon Herb Chicken
