In a large pan on the stove-top set to medium-high heat, add cooking oil. Brown the turkey. Add to the slow cooker. Add the marinara sauce, mushrooms, onion, garlic, salt, pepper, oregano, and basil to the slow cooker as well. Stir.
Cut the spaghetti squash in half, remove the seeds with a spoon.
Add the squash cut side down in the slow cooker into the sauce.
Cover and cook on HIGH for 4 hours. Do not open the lid during the cooking time.
Nutritional values are approximate, please your own calculations if you require a special diet.