
This Easy Squash Casserole Recipe is an old fashioned Southern classic casserole made with yellow squash, cheese, mayonnaise, and sour cream. Topped with crushed butter crackers, it's a 10-ingredient recipe that's guaranteed to be delicious.
Preheat oven to 350°F. Grease an 9"x9" pan or 2 quart baking dish with butter or cooking spray.
Melt 2 tablespoons of the butter in a large skillet over medium-high heat. Add the sliced squash and chopped onion to the skillet. Season with 1 teaspoon of the salt. Cook until the squash is tender, about 10 minutes. Gently stir occasionally. Pour in a colander to drain any excess moisture.
In a large bowl, combine sour cream, mayonnaise, 1/2 cup of the sharp cheddar cheese, half of the Swiss cheese, half of the Parmesan cheese, remaining salt, and black pepper.
Fold the cooked squash and onions into the creamy mixture. Once combined, fold the whisked egg into the mixture. Pour into the prepared baking dish.
Melt the remaining butter in a medium mixing bowl. Combine with crushed crackers and remaining cheeses. Evenly distribute on top of the squash base.
Bake in the preheated oven 20-25 minutes, or until bubbly and golden brown.