Tasty Yellow Squash Casserole

Here is my favorite healthy yellow squash casserole recipe, loaded with fresh summer squash, zucchini, kale, and quinoa, all baked together with herbs, cheese, and a crispy panko topping.

This casserole has become my go-to dish when I want something comforting but still packed with vegetables. It’s a great way to use up all that squash from the garden, and my family actually asks for seconds. Plus, leftovers taste even better the next day!

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What Kind of Yellow Squash Should I Use?

For this casserole, you’ll want to look for yellow squash that’s firm to the touch with smooth, bright skin and no soft spots or blemishes. Medium-sized squash (about 6-8 inches long) tend to have the best flavor and texture – they’re not too watery like the larger ones can be, and they have fewer seeds. You can use either straightneck or crookneck yellow squash for this recipe, as both varieties will work equally well. When you’re prepping your squash, there’s no need to peel it since the skin becomes tender during cooking and adds extra nutrients to your casserole.

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Options for Substitutions

This casserole is pretty forgiving, so feel free to make some swaps based on what you have:

• Curly kale: If kale isn’t your thing, try using spinach, Swiss chard, or collard greens instead. Spinach will cook down more, so you might want to use a bit extra.
• Yellow squash and zucchini: You can use all of one or the other if that’s what you have on hand. Other summer squash varieties work great too – just keep the total amount at 4 cups.
• Quinoa: Brown rice, white rice, or even farro make good substitutes here. Just make sure whatever grain you use is already cooked before mixing it in.
• Greek yogurt: Sour cream or cottage cheese (blended smooth) can replace the Greek yogurt. Regular yogurt works too, but Greek yogurt gives you more protein and a thicker texture.
• Fresh herbs: Don’t have fresh oregano and basil? Use 2 teaspoons dried oregano and 2 teaspoons dried basil instead. Add them when you’re cooking the vegetables so they have time to release their flavor.
• Panko: Regular breadcrumbs work fine, or you can make your own by pulsing stale bread in a food processor. For a gluten-free option, try crushed rice crackers or gluten-free breadcrumbs.

Watch Out for These Mistakes While Baking

The biggest mistake when making this casserole is not cooking off enough moisture from the vegetables, which can leave you with a watery dish – make sure the broth is completely evaporated and the squash releases most of its liquid during the stovetop cooking phase.

Another common error is cutting your squash and zucchini pieces too small, as they’ll turn mushy during baking, so stick to that 1/2 inch size and try to keep them uniform for even cooking.

Don’t skip letting the vegetable mixture cool for a few minutes before adding the egg and yogurt, since the heat can scramble the egg or make the yogurt separate.

Finally, if your casserole looks like it’s browning too quickly on top, tent it loosely with foil for the last 10-15 minutes of baking to prevent burning while the inside finishes cooking through.

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What to Serve With Yellow Squash Casserole?

This casserole is pretty hearty on its own since it’s packed with quinoa and veggies, but I love serving it alongside some grilled chicken or baked salmon for extra protein. A simple arugula salad with lemon vinaigrette cuts through the richness of the cheese and adds a nice peppery bite to the meal. If you want to keep things vegetarian, some warm garlic bread or a crusty baguette is perfect for scooping up any cheesy bits left on your plate. For a lighter option, roasted cherry tomatoes or a cucumber and tomato salad with fresh herbs works really well too.

Storage Instructions

Store: This casserole keeps really well in the fridge for up to 4 days. Just cover it tightly with foil or transfer it to an airtight container once it’s cooled down. The flavors actually get even better the next day as everything has time to meld together.

Freeze: You can freeze this casserole for up to 3 months, either as a whole dish or in individual portions. Let it cool completely, then wrap it well in plastic wrap and foil before freezing. Individual portions are great for quick weeknight dinners when you don’t feel like cooking.

Reheat: Warm it up in the oven at 350°F covered with foil until heated through, about 20-25 minutes from the fridge or 35-40 minutes from frozen. You can also microwave individual portions for 2-3 minutes, though the topping won’t be quite as crispy.

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 1450-1600
• Protein: 65-75 g
• Fat: 45-55 g
• Carbohydrates: 180-200 g

Ingredients

For the casserole:

• 1 tbsp olive oil
• 1/2 onion (finely diced into 1/4-inch pieces)
• 6 cups kale
• 2 tsp garlic
• 1/2 cup vegetable broth
• 2 cups yellow squash (sliced into 1/4-inch thick rounds)
• 2 cups zucchini (sliced into 1/4-inch thick rounds)
• 2 tbsp oregano
• 2 tbsp basil
• 1/2 tsp lemon zest
• 1/4 tsp red pepper flakes
• 2/3 cup Greek yogurt
• 2 cups cooked quinoa
• 1 cup mozzarella
• 1/2 cup parmesan
• 1 cup panko
• 1 egg (beaten)
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• cooking spray

For the topping:

• 3 tbsp panko
• 2 tbsp parmesan

Step 1: Prepare mise en place and preheat oven

• cooking spray
• 1/2 onion
• 2 cups yellow squash
• 2 cups zucchini
• 2 tsp garlic
• 6 cups kale
• 1 egg

Preheat your oven to 400°F and lightly coat a 9×13 inch baking dish with cooking spray.

While the oven heats, prepare all your ingredients: finely dice the onion into 1/4-inch pieces, slice the yellow squash and zucchini into 1/4-inch rounds, mince the garlic, measure out the kale, and beat the egg in a small bowl.

Having everything prepped and ready will make the cooking process smooth and prevent overcooking any components.

Step 2: Build the vegetable base with aromatics and greens

• 1 tbsp olive oil
• 1/2 onion
• 2 tsp garlic
• 6 cups kale
• 1/2 tsp salt
• 1/4 tsp black pepper
• 1/2 cup vegetable broth

Heat the olive oil in a large pot over medium heat, then add the diced onion and sauté for about 5 minutes until softened and fragrant.

Add the garlic, kale, salt, and black pepper, stirring constantly for about 1 minute to wilt the kale slightly.

Pour in the vegetable broth and simmer for 2-3 minutes until the broth has mostly reduced.

This gentle cooking builds a flavorful foundation without overcooking the delicate kale.

Step 3: Add and cook the summer squashes with herbs

• 2 cups yellow squash
• 2 cups zucchini
• 1/2 tsp salt
• 1/4 tsp black pepper
• 2 tbsp oregano
• 2 tbsp basil
• 1/2 tsp lemon zest
• 1/4 tsp red pepper flakes

Add the yellow squash and zucchini slices to the pot along with a pinch of additional salt and pepper.

Cook for 5-8 minutes, stirring occasionally, until the vegetables are just tender but still hold their shape—you want them cooked through but not mushy.

Remove from heat and stir in the oregano, basil, lemon zest, and red pepper flakes.

I prefer to add herbs at the end of cooking to preserve their bright, fresh flavors rather than cooking them down for too long.

Step 4: Create the binding mixture with cheese and binders

• cooked vegetable mixture from Step 3
• 2/3 cup Greek yogurt
• 2 cups cooked quinoa
• 1 cup mozzarella
• 1/2 cup parmesan
• 1 cup panko
• 1 egg

In a large mixing bowl, combine the cooked vegetable mixture from Step 3 with the Greek yogurt, cooked quinoa, mozzarella, parmesan, and 1 cup of panko.

Stir until everything is evenly distributed and well combined—the Greek yogurt and cheese will coat all the vegetables and grains.

Add the beaten egg and fold it in gently until the mixture is homogeneous.

The egg acts as a binder to help the casserole hold together when baked.

Step 5: Assemble and add the topping

• casserole mixture from Step 4
• 3 tbsp panko
• 2 tbsp parmesan

Transfer the entire mixture from Step 4 into your prepared 9×13 inch baking dish, spreading it evenly with a spatula.

In a small bowl, combine the 3 tablespoons of panko and 2 tablespoons of parmesan, then sprinkle this mixture evenly over the top of the casserole.

I like to gently press the topping down slightly so it gets golden and crispy during baking rather than staying loose and fluffy.

Step 6: Bake until golden and set

Bake in your preheated 400°F oven for 30-35 minutes, until the top is golden brown and the casserole is heated through.

The casserole is ready when the top is lightly browned and a knife inserted into the center comes out hot.

Let it rest for 5 minutes before serving—this allows the casserole to set and makes it easier to portion and serve.

Tasty Yellow Squash Casserole

Delicious Tasty Yellow Squash Casserole recipe with step-by-step instructions.

Print Recipe Pin Recipe

Prep Time 20 minutes mins

Cook Time 40 minutes mins

Total Time 1 hour hr 2 minutes mins

Servings 6 servings

Calories 1525 kcal

Ingredients

  

For the casserole

• 1 tbsp olive oil
• 1/2 onion (finely diced into 1/4-inch pieces)
• 6 cups kale
• 2 tsp garlic
• 1/2 cup vegetable broth
• 2 cups yellow squash (sliced into 1/4-inch thick rounds)
• 2 cups zucchini (sliced into 1/4-inch thick rounds)
• 2 tbsp oregano
• 2 tbsp basil
• 1/2 tsp lemon zest
• 1/4 tsp red pepper flakes
• 2/3 cup Greek yogurt
• 2 cups cooked quinoa
• 1 cup mozzarella
• 1/2 cup parmesan
• 1 cup panko
• 1 egg (beaten)
• 1/2 teaspoon salt
• 1/4 teaspoon black pepper
• cooking spray

For the topping

• 3 tbsp panko
• 2 tbsp parmesan

Instructions

 

• Preheat your oven to 400°F and lightly coat a 9x13 inch baking dish with cooking spray. While the oven heats, prepare all your ingredients: finely dice the onion into 1/4-inch pieces, slice the yellow squash and zucchini into 1/4-inch rounds, mince the garlic, measure out the kale, and beat the egg in a small bowl. Having everything prepped and ready will make the cooking process smooth and prevent overcooking any components.
• Heat the olive oil in a large pot over medium heat, then add the diced onion and sauté for about 5 minutes until softened and fragrant. Add the garlic, kale, salt, and black pepper, stirring constantly for about 1 minute to wilt the kale slightly. Pour in the vegetable broth and simmer for 2-3 minutes until the broth has mostly reduced. This gentle cooking builds a flavorful foundation without overcooking the delicate kale.
• Add the yellow squash and zucchini slices to the pot along with a pinch of additional salt and pepper. Cook for 5-8 minutes, stirring occasionally, until the vegetables are just tender but still hold their shape—you want them cooked through but not mushy. Remove from heat and stir in the oregano, basil, lemon zest, and red pepper flakes. I prefer to add herbs at the end of cooking to preserve their bright, fresh flavors rather than cooking them down for too long.
• In a large mixing bowl, combine the cooked vegetable mixture from Step 3 with the Greek yogurt, cooked quinoa, mozzarella, parmesan, and 1 cup of panko. Stir until everything is evenly distributed and well combined—the Greek yogurt and cheese will coat all the vegetables and grains. Add the beaten egg and fold it in gently until the mixture is homogeneous. The egg acts as a binder to help the casserole hold together when baked.
• Transfer the entire mixture from Step 4 into your prepared 9x13 inch baking dish, spreading it evenly with a spatula. In a small bowl, combine the 3 tablespoons of panko and 2 tablespoons of parmesan, then sprinkle this mixture evenly over the top of the casserole. I like to gently press the topping down slightly so it gets golden and crispy during baking rather than staying loose and fluffy.
• Bake in your preheated 400°F oven for 30-35 minutes, until the top is golden brown and the casserole is heated through. The casserole is ready when the top is lightly browned and a knife inserted into the center comes out hot. Let it rest for 5 minutes before serving—this allows the casserole to set and makes it easier to portion and serve.