All you need is fifteen minutes of prep time to make this all-in-one meal--perfect for those days when you need something easy but still cozy and comforting.
Preheat oven to 425°. Halve squash lengthwise; remove seeds. Brush cut sides with olive oil. Place squash cut sides down on a parchment-lined baking sheet. Bake 20 minutes.
Meanwhile, in a skillet, brown sausage. Add onion; cook 3 minutes. Add apple and celery; cook 3 minutes. Stir in wild rice; cook 1 minute.
Turn squash halves over. Spoon sausage mixture into squash; top with walnuts. Bake 10 minutes more.