- 1 pound yellow squash, sliced
- 1 pound zucchini, sliced
- 1/2 onion, diced
- 1 cup shredded Cheddar cheese
- 1/2 cup biscuit baking mix (such as Bisquick®)
- 1/2 cup butter
- 2 eggs
- 1 tablespoon white sugar
- 1 teaspoon salt
- 10 saltine crackers, or as needed, crushed
- 1/4 cup bread crumbs
- Preheat oven to 325 degrees F (165 degrees C).
- Fill a large pot with water and bring to a rolling boil. Add yellow squash, zucchini, and onion; bring back to a boil, and cook vegetables until tender, about 15 minutes. Drain and transfer vegetables to a large bowl.
- Mix Cheddar cheese, baking mix, butter, eggs, sugar, and salt with the cooked vegetables using a large spoon; stir until butter has melted and baking mix has dissolved. Fold crushed crackers into the mixture until the liquid has been absorbed. Pour mixture into a 1 1/2-quart casserole dish; top with bread crumbs.
- Bake in the preheated oven until topping is lightly browned and cheese is melted, 30 minutes.