Preheat oven to 400°F. Line a baking sheet with aluminum foil.
Place squash, cut side up, on prepared baking sheet. Drizzle with olive oil and sprinkle with salt and pepper. Bake for 30 to 45 minutes, or until flesh is tender.
In a skillet over medium heat, brown sausage. When cooked thoroughly, add apples and stir until fruit is softened. Season with salt and pepper.
Stuff cooked squash cavity with sausage mixture. Bake for 10 to 15 minutes more. Cool slightly before serving.