To prepare a spaghetti squash and chicken skillet casserole casseroles recipe, you will first need to prepare your ingredients. You will need: Spaghetti squash: Preheat the oven to 400 degrees F (204 degrees C). Cut the squash in half lengthwise and scoop out the seeds. Peel the skin and cut the flesh into 1/4-inch cubes. Add the cubed flesh to the casserole dish and toss to coat. Bake in the preheated oven for 20 to 25 minutes or until the cheese is melted and bubbling. Remove from oven and let stand for 5 minutes before serving.