Chicken Zucchini Casserole Recipe: Cheesy Baked Dinner for Summer Squash Season

By Aquarium Guides Editorial Team · Updated November 10, 2026

Last Updated: November 10, 2026

When the garden or the market hands you more zucchini than you know what to do with, this chicken zucchini casserole is a reliable answer. Tender chicken, sliced zucchini, a creamy sauce, and a crisp topping bake together in one dish. The main challenge with any zucchini casserole is excess water, so this recipe includes a simple step to draw moisture out before baking. Prep takes about 25 minutes and the oven does the rest.

Ingredients

Casserole

• 1 1/2 pounds boneless, skinless chicken breasts, cut into 3/4-inch pieces
• 1 teaspoon kosher salt, divided, plus 1 teaspoon for the zucchini
• 1/2 teaspoon black pepper
• 1 teaspoon garlic powder
• 1 teaspoon dried Italian seasoning
• 3 medium zucchini (about 1 1/2 pounds), sliced into 1/4-inch half-moons
• 2 tablespoons olive oil
• 1 small yellow onion, diced
• 3 cloves garlic, minced
• 2 tablespoons all-purpose flour
• 1 cup chicken broth
• 3/4 cup sour cream
• 1 1/2 cups shredded mozzarella, divided
• 1/2 cup grated Parmesan, divided

Crunchy Topping

• 1 cup panko breadcrumbs
• 2 tablespoons melted butter
• 1/4 teaspoon paprika
• 1 tablespoon chopped fresh parsley

Instructions

1. Toss the sliced zucchini with 1 teaspoon salt in a colander. Let it drain for 20 minutes, then press gently between clean kitchen towels to remove moisture.
2. Heat the oven to 375°F. Grease a 9×13-inch baking dish.
3. Season the chicken with 1/2 teaspoon salt, pepper, garlic powder, and Italian seasoning.
4. Heat 1 tablespoon olive oil in a large skillet over medium-high heat. Cook the chicken for 5 to 6 minutes, stirring occasionally, until browned and nearly cooked through. Transfer to a bowl.
5. Add the remaining oil to the skillet. Cook the onion for 3 minutes, then add the garlic for 30 seconds.
6. Sprinkle the flour over the onion and stir for 1 minute. Slowly pour in the broth, whisking, and simmer 2 to 3 minutes until thickened.
7. Remove from the heat. Stir in the sour cream, 1 cup mozzarella, 1/4 cup Parmesan, and the remaining 1/4 teaspoon salt.
8. Fold in the chicken and zucchini. Spread everything into the baking dish.
9. Mix the panko, butter, paprika, parsley, and remaining Parmesan. Scatter over the top along with the remaining 1/2 cup mozzarella.
10. Bake uncovered for 30 to 35 minutes, until bubbling and golden and the chicken reads 165°F in the center.
11. Rest 10 minutes before serving so the sauce can set.

Why Salting the Zucchini Matters

Zucchini is mostly water. Without a salting step, it releases liquid in the oven and turns the sauce thin and watery. Salting draws out moisture through osmosis, and pressing the slices removes much of it. The slices still keep a tender, not mushy, bite after baking. If you are short on time, you can skip the full 20 minutes and let them sit for 10, but the longer rest gives the best texture.

Tips

• Cut zucchini into uniform slices so they cook evenly. A mandoline helps.
• Pre-cooking the chicken lightly adds flavor from browning, but make sure it finishes at 165°F in the oven.
• Use full-fat sour cream. Low-fat versions are more likely to separate in the oven heat.
• Let the casserole rest before cutting; otherwise the sauce runs.
• For deeper color on top, broil for 1 to 2 minutes at the end, watching closely.
• Use a thermometer in several places, including near the center, to confirm safe temperature.

Variations

Rotisserie Chicken Shortcut

Use 3 cups of shredded rotisserie chicken in place of raw chicken. Skip the browning step and reduce the bake time to 25 minutes, just until hot and bubbly.

Tex-Mex Style

Swap Italian seasoning for chili powder and cumin, use pepper jack cheese, and stir in a drained can of black beans and 1 cup of corn. Top with crushed tortilla chips.

Low-Carb Topping

Replace the panko with crushed pork rinds mixed with Parmesan for a crunchy, grain-free finish.

Cream of Chicken Shortcut

Replace the flour, broth, and sour cream with one can of condensed cream of chicken soup mixed with 1/2 cup sour cream. It is less work but adds sodium, so reduce the added salt.

Mixed Summer Squash

Use a mix of green zucchini and yellow summer squash for color. Both take the same treatment.

Tomato and Basil

Layer in 1 cup of halved cherry tomatoes and 1/4 cup torn basil for a lighter, brighter flavor.

Choosing and Prepping Zucchini

Small to medium zucchini, about 6 to 8 inches long, have firmer flesh and fewer seeds than oversized ones. If you have a baseball-bat-sized zucchini from the garden, halve it lengthwise and scoop out the spongy seed center with a spoon before slicing. Choose squash that feels heavy for its size with glossy, unblemished skin. Store it unwashed in the refrigerator crisper drawer and use within a week.

Timing Guide

• Salting and draining zucchini: 20 minutes (do other prep while it sits)
• Browning chicken and building sauce: 15 minutes
• Baking: 30 to 35 minutes
• Resting: 10 minutes

Total time from start to table is about 90 minutes, but only 30 minutes of that is active cooking. For a faster weeknight version, use rotisserie chicken and skip the salting step by sauteing the zucchini for 4 to 5 minutes in a hot skillet to drive off moisture instead.

Serving Ideas

A crisp green salad with lemon vinaigrette is a good partner. For heartier appetites, serve over rice, orzo, or buttered noodles, or spoon onto toasted sourdough. Because the casserole is saucy, crusty bread is useful for catching every last bit.

Storage and Reheating

Cool the casserole and refrigerate within 2 hours in a covered container. It keeps well for 3 to 4 days. Reheat individual portions in the microwave for 1 to 2 minutes or the whole dish covered with foil at 350°F for 20 to 25 minutes, until it reads 165°F. The topping softens as it sits, so sprinkle fresh panko over the leftovers and broil briefly to revive some crunch.

To freeze, assemble without the breadcrumb topping, wrap tightly, and freeze up to 2 months. Thaw in the refrigerator overnight, add the topping, and bake until heated through and the center reaches 165°F. Zucchini releases a bit more water after freezing, so draining the dish slightly before topping can help.

FAQ

Why is my zucchini casserole watery?

The zucchini most likely released water during baking. Salt and press the slices before assembling, and do not cover the dish while it bakes, so steam can escape.

Can I prepare this casserole ahead of time?

Yes. Assemble everything except the topping, cover, and refrigerate up to 24 hours. Add the topping just before baking and extend the time by about 10 minutes since it starts cold.

Do I need to peel the zucchini?

No. The skin is thin and softens in the oven. Wash it well and trim the ends.

Can I use frozen zucchini?

Thaw it completely and squeeze out as much water as possible with a towel. Frozen zucchini tends to be softer, so it works better in a casserole with a thicker sauce.

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