Chicken Zucchini Casserole

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Casseroles are some of my favorite healthy dinners because you only need to make one dish—no need for a separate main and side. And even though my chicken zucchini casserole has some pre-cooking steps (as casseroles often do), I still love the simplicity of this one-recipe meal. And the perfect excuse to use more zucchini. And the cheesy gruyere sauce that totally feels like comfort food. Make it with me and make the most of zucchini season!

Why You Need My Chicken Zucchini Casserole

• Luscious gruyere cheese sauce – The sauce is what sets this one apart from your run-of-the-mill chicken casserole. You’ll love the rich, cheesy, and bold flavor! It doesn’t look like a lot of sauce because the veggies absorb some of it, but make no mistake, you can taste it in every bite!
• Never watery – If you’ve made my standalone zucchini casserole before, you know I won’t settle for anything less. This time I use a different method, but the texture is just as important. Don’t miss my tips below!
• Easy, healthy meal – The steps are straightforward, the ingredients are fresh and simple, and it’s packed with protein and veggies. Plus, it’s meal prep friendly, so you can even enjoy my chicken zucchini casserole on busy weeknights. You don’t need any sides, but you could start with a soup or salad, or finish off your meal with my summery cherry crisp.

Ingredients & Substitutions

Here I explain the best ingredients for my chicken zucchini casserole recipe, what each one does, and substitution options. For measurements, see the recipe card.

Main Ingredients:

• Chicken – I usually use boneless skinless chicken breast, but boneless chicken thighs also work. Cut the chicken into 1-inch pieces. Or if you’ve got leftover chicken bites, Instant Pot shredded chicken, or even a rotisserie chicken, feel free to use those — and save time by skipping the pan searing step.
• Vegetables – I used sautéed mushrooms, onions, and of course, zucchini. Yellow squash actually works just as well instead of zucchini. You can also toss in bell peppers or broccoli if you like.
• Olive Oil – For searing the chicken and sauteing the veggies. Avocado oil works just as well.
• Sea Salt & Black Pepper

VARIATION: Add garlic for more flavor!

I didn’t add garlic in my casserole, but feel free to add 2-4 cloves of minced garlic—just sauté them with the onions and mushrooms.

Cheese Sauce:

• Shredded Cheese – The star of my chicken zucchini casserole is the Swiss Gruyere cheese blend! I love the nutty, slightly sweet flavor. If you can’t find a blend, you can just shred both cheeses yourself. If you prefer a milder flavor, swap in a combo of parmesan and mozzarella cheese instead.
• Heavy Cream – This makes the sauce rich and creamy. If you’re looking for a lighter option, you can substitute with half-and-half or whole milk, but the sauce will be less thick.
• Chicken Broth – You can use my homemade chicken broth or a reduced-sodium store-bought version. If all you have is regular, I recommend using less salt on your chicken and veggies.
• Sour Cream – For more richness and tang. Greek yogurt works well as a substitute. Cream cheese can also work, but you might need a splash of extra cream, since it’s thicker.

How To Make Chicken Zucchini Casserole

I have step-by-step photos here to help you visualize the recipe. For full instructions with amounts and temperatures, see the recipe card.

1. Season & dry the chicken. Place the chicken pieces in a large bowl and pat dry with paper towels. Season with salt and pepper.
2. Cook the chicken. Heat olive oil in a large skillet over medium-high. Add the chicken pieces and sear, turning to brown all sides until cooked through. Transfer to a bowl and cover to keep warm.

3. Sauté the mushrooms & onions. Add more olive oil to the pan, reduce the heat, and add the mushrooms and onions. Cook until the mushrooms are soft and there is no liquid in the pan.
4. Cook the zucchini. Turn the heat to medium-high again, add the zucchini, and season with salt and pepper. Sauté until soft and slightly browned, then drain any remaining liquid. Transfer to the bowl with the chicken and set aside.

5. Make the sauce. While your oven preheats, add the heavy cream and chicken broth to the same skillet. Scrape up any browned bits with a wooden spoon. Simmer for about 5 minutes, until the sauce coats the back of a spoon. Then, stir in shredded cheese, until melted.

6. Assemble & bake. Pour the sauce into the bowl with the chicken and veggies. Mix to combine, then transfer the mixture to a small baking dish (I use this one and it’s the perfect size). Sprinkle more shredded cheese on top. Bake the chicken zucchini casserole until the cheese on top is melted. If you like it browned more (highly recommend!), place under the broiler.

My Recipe Tips

I’ve been making this chicken zucchini casserole since 2018, but I made some tweaks to the recipe recently to improve it. And I discovered some additional tips along the way:

• Browning and stovetop temp depends on your pan. I use cast iron and sometimes need to turn it down, but with nonstick you may need the heat even higher.
• Use lower heat if you don’t want your chicken to darken. I like mine golden, but you can choose medium heat if you like less browning.
• It’s important to cook down the zucchini and mushrooms enough and let all the liquid evaporate. If you don’t, the casserole will be watery. If the zucchini starts to brown too much, reduce heat to medium but continue cooking to get it tender. If it’s crisp, it will release water when you bake the chicken zucchini casserole.
• Drain the chicken and veggies if needed. Sometimes the veggies still release more moisture as they sit while I make the sauce. If this happens, drain them again before mixing in the sauce.
• Save time by multitasking. I cut the zucchini while the mushrooms and onions cook, then make the Gruyere cheese sauce while the oven preheats.
• Do not use a whisk to mix in the shredded cheese. The cheese will clump on the whisk. I’ve found that a wooden spoon works best for this.
• Salt the sauce to taste. I didn’t need additional salt in the sauce, but this will vary depending on the broth and cheese brands you use.

Storage & Meal Prep

• Store: Keep leftovers in an airtight container in the refrigerator for up to 3-4 days. The veggies do get more mushy, but the flavor is still great.
• Meal prep: This chicken and zucchini casserole does have several steps, but it’s a breeze if you prep ahead! You can either just do the chopping in advance, or assemble the whole thing and keep it in the fridge (for 1-2 days) until ready to bake.
• Reheat: Just pop it in the oven for 15-20 minutes at 350 degrees F. The microwave works for individual portions if you’re in a hurry.
• Freeze: The assembled casserole freezes well for up to 3 months. You can reheat it from frozen at 350 degrees F, but this takes a long time (at least 45 minutes), so I usually thaw it in the fridge overnight for quicker heating.

More Cheesy Casserole Recipes

If you’re a fan of easy, cheesy casseroles like this, you’ll love my others:

Chicken Bacon Ranch Casserole

Loaded Cauliflower Casserole

Pepperoni Pizza Casserole

Cheesy Broccoli Casserole

Tools I Use For This Recipe

• Casserole Dish – My favorite brand. This one is a little smaller than your standard baking dish, but it’s the perfect size for this recipe. You can use a larger one, but it will be less full.
• Cast Iron Skillet – You need a big skillet to fit all those veggies before they cook down! And I love my cast iron for the best browning and evaporating extra moisture.

Recipe Card

4.79 from 64 votes

Chicken Zucchini Casserole

By Maya Krampf

This chicken zucchini casserole has a rich cheese sauce, plus more melty cheese on top! My easy cooking method keeps it from getting watery.

Prep: 10 minutes

Cook: 40 minutes

Total: 50 minutes

Servings: 5 (adjust to scale recipe)

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Recipe Video

Ingredients

[ See substitutions ]

U.S. – Metric

Tap underlined ingredients to see the ones I use.

• 1 lb Boneless skinless chicken breast (cut into 1-inch pieces) ▢
• 3/4 tsp Sea salt (divided into 1/2 tsp and 1/4 tsp) ▢
• 1/2 tsp Black pepper (divided) ▢
• 2 tbsp Olive oil (divided) ▢
• 8 oz Mushrooms (sliced) ▢
• 1/2 large Onion (diced) ▢
• 3 medium Zucchini (cut into half-moons) ▢
• 1/2 cup Heavy cream ▢
• 1/3 cup Chicken broth, reduced sodium ▢
• 6 oz Swiss Gruyere shredded cheese blend (or just one of the two types; divided) ▢
• 1/2 cup Sour cream ▢

Instructions

[ See step photos • See my tips ]

Tap on the times in the instructions to start a kitchen timer.

Cook The Chicken:

1. Place the chicken pieces in a large bowl and pat dry with paper towels. Season with 1/2 teaspoon of salt and 1/4 teaspoon of pepper.

2. Heat 1 tablespoon of olive oil in a 12-inch skillet over medium-high heat. Add the chicken pieces and sear for 5-6 minutes, turning every couple of minutes to brown all sides, until cooked through. Remove the chicken to a large bowl, cover to keep warm, and set aside.

Cook The Veggies:

1. Add the remaining 1 tablespoon of olive oil to the pan and reduce heat to medium. Add the mushrooms and onions. Cook for 7-10 minutes, until the mushrooms are soft and there is no liquid in the pan.

2. Increase heat to medium-high. Add the zucchini. Season the vegetables with the remaining 1/4 teaspoon of salt and 1/4 teaspoon of pepper. Saute, stirring occasionally, for about 10 minutes, uncovered, until the zucchini is soft and a little browned. Most (if not all) of the liquid should evaporate.

3. Drain the veggies if any liquid remains and transfer to the bowl with the chicken. Set aside.

Make The Sauce:

1. Preheat the oven to 400 degrees F (191 degrees C).

2. While the oven preheats, add cream and chicken broth to the same skillet. Scrape the bottom of the pan with a wooden spoon to release any browned bits. Turn on the heat to medium-high and bring to a boil, then simmer for about 5 minutes, until thick enough to thinly coat the back of a spoon.

3. Reduce heat to low. Stir 3 ounces of the shredded cheese into the pan, until melted.

4. Remove from heat. Stir in the sour cream. If needed, season the sauce with salt and pepper to taste.

Assemble & Bake:

1. If any additional liquid has formed in the bowl with the zucchini and chicken, drain it. Then, pour the sauce into the bowl with the chicken and veggies. Mix to combine.

2. Transfer the mixture to a 10×7-inch casserole dish. Sprinkle the remaining 3 ounces of shredded cheese on top.

3. Bake for about 10 minutes, until the cheese on top is melted. If desired, place under the broiler for 2-3 minutes to brown the cheese on top.

Did you make it? Leave a review or tag me @wholesomeyum on Instagram!

Maya’s Recipe Notes

Serving size: 1 cup

Nutrition Facts

Amounts per serving. Serving size in recipe notes above.

Calories 451

Fat 32g

Protein 33g

Total Carbs 9g

Net Carbs 7.1g

Fiber 1.9g

Sugar 5.9g

I provide nutrition facts as a courtesy. Have questions about calculations or why you got a different result? Please see my nutrition policy.

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Try More Of My Recipes

• 
  Chicken Cordon Bleu Casserole
• 
  Cauliflower Mac and Cheese
• 
  Yellow Squash Casserole
• 
  Big Mac Casserole

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Gratitude Moment

I just got back from a trip to sunny San Diego and didn’t even realize how much I needed a “real” vacation until it hit me. I travel a lot, but it’s always go, go, go — and a lot of it is for work.

This time, a group of my girl friends all went together for a relaxing weekend. And unlike most of our family trips that are pretty planned out, we just did whatever we felt like last-minute. It was just what I needed — even if it meant coming back to a 12-hour recipe photo shoot the next day. 😉

I did bring back a “lovely” sunburn, because clearly I underestimated the California sun with my SPF. It was worth it.