Zucchini, Yellow Squash and Quinoa Casserole is a flavorful way to use a summer harvest of zucchini and yellow squash. Versatile as a side or a satisfying meatless main, this casserole combines tender sautéed squash with protein-rich quinoa, melty cheese and a crisp breadcrumb topping. The texture is creamy, the flavors are fresh, and it’s well worth heating the oven for.
The inspiration behind this recipe:
Every summer our garden produces an abundance of summer squash, and I like to revisit favorite seasonal dishes while also experimenting with new ideas. This casserole was created to use a large amount of zucchini and yellow squash in a way that preserves their delicate flavor—without boiling—and highlights quinoa’s nutty protein boost. The result is a comforting, vegetable-forward casserole that feeds a family or a crowd.
Because the squash often peaks while I’m away, I developed this recipe to be forgiving and easy to scale. It works with slightly more of one squash than the other, and the mixture holds up well if you prepare it ahead of time or freeze it for later.
How to make Zucchini, Yellow Squash and Quinoa Casserole
- Begin with approximately three pounds of summer squash—about 1 1/2 pounds zucchini and 1 1/2 pounds yellow squash, or any mix close to that amount.
- Slice the squash into roughly 1/4-inch rounds so they cook evenly and retain texture.
- Saute the squash with chopped onion until it softens. Avoid boiling the squash; sautéing preserves the delicate flavor and prevents it from becoming waterlogged.
After sautéing, the cooked vegetables are combined with cooked quinoa, diced green chiles for gentle heat, shredded cheese, sour cream, mayonnaise and eggs to create a rich, cohesive filling. A topping of panko breadcrumbs, grated Parmesan (or Asiago) and a little butter gives a satisfying crunch after baking.
- Mix the cooled vegetables with 3 cups of cooked quinoa and 2 cups of shredded white Cheddar or Monterey Jack cheese.
- Whisk together 3/4 cup sour cream, 3/4 cup mayonnaise and 2 large eggs, then fold into the vegetable-quinoa mixture.
- Spread the mixture into a prepared 13 x 9-inch baking dish and top evenly with a crumb mixture made from 1 cup panko, 1/2 cup freshly grated Parmesan (or Asiago) and the remaining butter.
- Bake uncovered at 350°F until set and golden, about 45–50 minutes.
The finished casserole balances creamy interior textures with a crisp topping and delivers a comforting, flavorful plate that showcases summer squash and whole grain quinoa. It pairs well with a simple green salad or can be served as a standalone vegetarian entree.
More vegetarian casseroles you might like:
- Black Bean and Yellow Squash Enchilada Casserole
- Yellow Squash and Tomato Gratin with Two Cheeses
- Southwestern Lentil and Brown Rice Bake
- Summer Squash, Corn and Poblano Casserole
- Summer Vegetable Parmigiana
- Brown Rice Cheddar Kale Casserole
- Zucchini Corn Casserole
- Cheesy Brown Rice and Greens Casserole
- Classic Summer Squash Casserole
Zucchini Yellow Squash and Quinoa Casserole
A creamy, cheese-forward casserole featuring sautéed zucchini and yellow squash, protein-rich quinoa, green chiles and a golden panko-Parmesan topping. Serves about 8.
Prep Time: 15 mins • Cook Time: 1 hr 15 mins • Total Time: 1 hr 30 mins • Servings: 8
Author: Carol | From A Chef’s Kitchen
Equipment
- Chef’s knife
- Cutting board
- Saucepan (for quinoa)
- Large skillet or sauté pan
- 13 x 9-inch baking dish
Ingredients
- Cooking spray or oil for the baking pan
- 2 tablespoons canola oil
- 4 tablespoons butter (1/2 stick), divided
- 1 medium onion, chopped
- 1 1/2 pounds zucchini, sliced into 1/4-inch slices
- 1 1/2 pounds yellow squash, sliced into 1/4-inch slices
- 4 cloves garlic, minced
- 2 cans (4-ounce each) diced green chiles, drained (hot or mild)
- 3 cups cooked quinoa
- Salt and freshly ground black pepper, to taste
- 2 cups shredded white Cheddar cheese or Monterey Jack
- 3/4 cup sour cream
- 3/4 cup mayonnaise
- 2 large eggs
- 1 cup panko breadcrumbs
- 1/2 cup freshly grated Parmesan cheese or Asiago
Instructions
- Preheat the oven to 350°F. Lightly oil or spray a 13 x 9-inch baking dish and set aside.
- Heat 2 tablespoons canola oil and 2 tablespoons butter in a large skillet over medium-high heat. Add the chopped onion, reduce the heat to medium and cook 5–6 minutes until it begins to soften.
- Add the sliced zucchini and yellow squash to the pan and continue to cook over medium heat for another 5–6 minutes until they begin to soften but still hold their shape.
- Add the minced garlic and cook about 15 seconds until fragrant. Remove the pan from the heat and let the vegetables cool slightly.
- Transfer the cooled vegetables to a large bowl. Stir in the drained green chiles, cooked quinoa and shredded cheese. Season with salt and freshly ground black pepper to taste.
- In a small bowl whisk together the sour cream, mayonnaise and eggs. Fold this mixture into the vegetable, quinoa and cheese blend until combined.
- Transfer the mixture into the prepared baking dish and spread evenly.
- In a small bowl combine the remaining 2 tablespoons butter (melted), panko breadcrumbs and grated Parmesan or Asiago. Sprinkle evenly over the top of the casserole.
- Bake uncovered for 45–50 minutes, until the top is golden brown and the casserole is set. Let rest a few minutes before serving.
Notes
Make-ahead: Assemble the casserole up to the point of adding the breadcrumb topping, cover and refrigerate. Add the topping and bake when ready.
Freezer-friendly: Freeze before or after baking for 1–2 months. Thaw in the refrigerator and reheat in a 350°F oven until warmed through.
Nutrition (per serving)
Calories: 527 kcal • Carbohydrates: 30 g • Protein: 18 g • Fat: 38 g • Fiber: 4 g
Nutritional values are estimates and will vary based on specific ingredients and portion sizes.
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