Easy Zucchini and Squash Casserole

When summer vegetables are plentiful, this zucchini and squash casserole is one of the easiest ways to turn them into a comforting side dish the whole family can enjoy. Tender slices of zucchini and yellow squash are seasoned with garlic and herbs, layered with cheese, and finished with a crisp Parmesan and panko topping.

The recipe is simple enough for a weeknight but also works beautifully alongside a larger family dinner or holiday meal. Unlike heavier squash casseroles, this version lets the vegetables remain the star of the dish.

The most important part is controlling the moisture in the zucchini and yellow squash. A quick salting and draining step helps prevent a watery casserole and gives you tender vegetables with a golden, cheesy topping.

Why You’ll Love This Zucchini and Squash Casserole

This casserole uses simple ingredients while delivering plenty of flavor and texture.

Fresh vegetables. Zucchini and yellow squash make up most of the casserole, so it’s an easy way to serve more vegetables with dinner.

Cheesy and comforting. Mozzarella melts between the vegetables while Parmesan adds a savory finish.

Crispy topping. Panko breadcrumbs give the top a light crunch without hiding the zucchini and squash underneath.

No canned soup. The recipe doesn’t rely on condensed cream soup to hold everything together.

Easy side dish. It pairs well with chicken, beef, rice, and many other family dinners.

Great for summer. This is particularly useful when zucchini and yellow squash are abundant.

Ingredients You’ll Need

You only need a relatively short list of ingredients for this zucchini and squash casserole.

Zucchini: Choose firm medium zucchini without soft spots. Medium vegetables are easier to slice evenly and usually contain less water than oversized zucchini.

Yellow squash: Yellow summer squash adds color and a slightly different flavor while keeping the same tender texture.

Salt: Salting the sliced vegetables before baking helps draw out excess moisture.

Olive oil: A small amount helps the vegetables cook and carries the garlic and seasonings throughout the casserole.

Garlic: Fresh minced garlic adds savory flavor without overpowering the squash.

Italian seasoning: An easy combination of herbs that complements both zucchini and yellow squash.

Black pepper: Adds mild seasoning.

Mozzarella: Provides the creamy melted cheese between the vegetables.

Parmesan: Adds a stronger savory flavor and helps the topping brown.

Panko breadcrumbs: Create a crisp, light topping that contrasts with the tender squash.

The Secret to Avoiding a Watery Squash Casserole

Zucchini and yellow squash naturally contain a lot of water. As they cook, some of that moisture is released.

If all that liquid ends up in the baking dish, the casserole can become watery rather than tender and cheesy.

There’s an easy solution.

Slice the zucchini and yellow squash into approximately 1/4-inch rounds, sprinkle them lightly with salt, and leave them in a colander for about 15 minutes.

Then spread the slices over clean kitchen towels or paper towels and pat them thoroughly dry.

This small extra step makes a noticeable difference in the finished casserole.

How to Make Zucchini and Squash Casserole

1. Slice the Vegetables

Wash and dry the zucchini and yellow squash.

Trim the ends, then cut both vegetables into approximately 1/4-inch rounds.

Try to keep the slices similar in thickness so they cook evenly.

2. Salt and Drain

Place the sliced zucchini and yellow squash in a large colander.

Sprinkle them with salt and gently toss.

Allow them to sit for about 15 minutes.

Transfer the vegetables to clean kitchen towels or paper towels and pat them thoroughly dry.

3. Preheat the Oven

Preheat the oven to 400°F (205°C).

Lightly grease a 9×13-inch baking dish.

4. Season the Vegetables

Place the dried zucchini and yellow squash in a large bowl.

Add the olive oil, minced garlic, Italian seasoning, and black pepper.

Toss gently until the slices are evenly coated.

5. Assemble the Casserole

Arrange half of the seasoned zucchini and yellow squash in the prepared baking dish.

Sprinkle half of the mozzarella over the vegetables.

Add the remaining zucchini and squash, then top with the remaining mozzarella.

The vegetables don’t need to form perfectly straight rows. A slightly overlapping arrangement works well and keeps preparation simple.

6. Make the Crispy Topping

In a small bowl, combine the panko breadcrumbs and grated Parmesan.

Sprinkle the mixture evenly over the top of the casserole.

7. Bake

Bake uncovered for approximately 25–30 minutes, until the zucchini and yellow squash are tender and the cheese is melted.

The topping should be lightly golden.

For a little more browning, you can broil the casserole briefly at the end, watching it carefully so the topping doesn’t burn.

8. Rest Before Serving

Remove the casserole from the oven and allow it to rest for about 5 minutes.

This gives the vegetables and melted cheese a chance to settle before serving.

Tips for the Best Results

Don’t skip the draining step. Removing excess moisture is particularly important when cooking zucchini in a casserole.

Slice evenly. Vegetables with similar thickness will finish cooking at approximately the same time.

Pat the vegetables dry. Salting draws moisture to the surface, but you still need to remove that moisture before assembling the casserole.

Don’t overdo the cheese. We want this recipe to remain a zucchini and squash casserole rather than turning into mostly cheese.

Use freshly grated Parmesan when possible. It melts and browns particularly well in the panko topping.

Watch closely when broiling. Breadcrumbs and Parmesan can go from golden to burned quickly.

Zucchini vs. Yellow Squash

Zucchini and yellow squash are both types of summer squash and work particularly well together in casseroles.

Green zucchini usually has a straight shape and mild flavor.

Yellow squash has a similar tender texture but adds bright yellow color to the casserole. Some varieties have a slightly narrower, curved neck.

Using both makes the finished dish visually more interesting while keeping the preparation simple.

You can adjust the proportions depending on what you have available, but using approximately equal quantities produces a nice balance.

Zucchini and summer squash are classic warm-season vegetables, and the USDA highlights both among common late-summer produce

Can I Make This Casserole Without Panko?

Yes.

The panko provides crunch, but the casserole can still be made without it.

You can simply finish the vegetables with Parmesan and mozzarella for a completely cheesy topping.

Regular breadcrumbs can also replace panko, although the finished topping may be slightly finer and less crisp.

If you’re looking specifically for a richer cracker-topped casserole, make my Easy Squash Casserole with Ritz Crackers instead. That recipe has a different texture and flavor profile from this zucchini version.

Easy Variations

Add More Parmesan

For a stronger savory flavor, increase the Parmesan slightly while keeping the mozzarella layer moderate.

Use Italian-Style Breadcrumbs

Seasoned breadcrumbs can replace plain panko. If you use them, adjust the additional seasonings because the breadcrumbs may already contain salt and herbs.

Add Onion

Thinly sliced onion can be cooked briefly before being added to the zucchini and squash.

Cooking it first gives it time to soften and prevents large pieces of firm onion in the finished casserole.

Add a Little Heat

A small pinch of crushed red pepper flakes works well with the garlic, Parmesan, and zucchini.

Try Another Cheese

Monterey Jack can replace some or all of the mozzarella if you want a slightly different flavor.

What to Serve with Zucchini and Squash Casserole

Because this recipe works primarily as a vegetable side dish, you can pair it with many different main courses.

For a complete casserole-style family dinner, our Easy Chicken and Vegetable Casserole combines tender chicken with colorful vegetables and a creamy homemade sauce.

You could also serve zucchini casserole alongside roasted chicken, grilled chicken, halal beef, rice, or a simple pasta dish.

If you’re planning a richer comfort-food dinner, Easy Poor Man Husband Casserole provides a hearty ground beef and noodle main dish that contrasts nicely with a vegetable side.

Can You Make Zucchini and Squash Casserole Ahead?

You can prepare some components ahead, but I prefer not to assemble the entire casserole too far in advance.

Zucchini continues to release moisture as it sits.

For the best texture, slice and salt the vegetables shortly before assembling the dish.

You can grate the cheese, prepare the Parmesan-panko mixture, and measure the seasonings earlier in the day. Store them separately until you’re ready to assemble and bake.

This approach saves preparation time without allowing excess liquid to accumulate in the casserole dish.

How to Store Leftovers

Allow the casserole to cool, then transfer leftovers to an airtight container or cover the baking dish tightly.

Refrigerate for up to 3–4 days.

Because zucchini continues to release some moisture during storage, you may notice a little liquid in the container. This is normal.

How to Reheat It

For the best texture, reheat the casserole in the oven at 350°F until warmed through.

The oven helps restore some crispness to the breadcrumb topping.

Individual portions can also be reheated in the microwave, although the topping will become softer.

Can You Freeze Zucchini and Squash Casserole?

You technically can, but this isn’t the casserole I would choose for freezer meal preparation.

Zucchini and yellow squash contain a lot of water. Freezing and thawing can soften their texture considerably and cause additional liquid to be released.

For that reason, this casserole is best enjoyed freshly baked or refrigerated for a few days.

If you need a casserole that’s better suited to make-ahead meal planning, our Easy Chicken and Broccoli Casserole with Rice is a more practical option.

Frequently Asked Questions

Do I Need to Peel Zucchini Before Making a Casserole?

No.

Zucchini skin is tender and completely edible. Leaving it on also gives the casserole its attractive green color.

Wash the zucchini thoroughly and trim the ends before slicing.

Do I Need to Peel Yellow Squash?

No.

Like zucchini, tender yellow summer squash doesn’t need to be peeled for this recipe.

Why Is My Zucchini Casserole Watery?

The most common reason is excess moisture from the vegetables.

Salting the sliced zucchini and squash, allowing them to drain, and then patting them dry before baking helps significantly.

Oversized zucchini can also contain more water, so medium zucchini are preferable.

Can I Use Only Zucchini?

Yes.

You can make the recipe entirely with zucchini. However, combining green zucchini with yellow squash gives the casserole more color and variety.

Can I Use Only Yellow Squash?

Yes. Replace the zucchini with an equal amount of yellow summer squash.

The cooking process remains essentially the same.

Should I Cover the Casserole While Baking?

No.

Bake it uncovered. Covering the dish traps steam, while we want excess moisture to escape and the Parmesan-panko topping to become golden.

How Do I Know When It’s Done?

The squash should be tender when pierced with a fork, the mozzarella should be completely melted, and the topping should be lightly golden.

Avoid baking far beyond that point because the vegetables can become excessively soft.

More Easy Casserole Recipes

If you enjoyed this yellow squash and zucchini casserole, there are several other easy dinners and side dishes to try.

For dinner rather than a side dish, Easy Marry Me Chicken Casserole combines pasta, chicken, sun-dried tomatoes, spinach, Parmesan, and mozzarella in a creamy sauce.

A Simple Way to Enjoy Summer Squash

This zucchini and squash casserole turns two simple summer vegetables into a warm, cheesy side dish without covering them in a heavy sauce.

Salting and drying the vegetables first helps control excess moisture, while mozzarella adds creaminess and the Parmesan-panko mixture provides a crisp golden finish.

Serve it alongside your favorite family dinner during zucchini season, bring it to a summer gathering, or keep it in your recipe collection whenever you need an easy vegetable casserole.

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