Heat cooking spray in a large skillet over medium-high heat. Remove sausages from casing and place in skillet with chopped onion, breaking the sausage apart as it cooks. Cook until sausage is no longer pink. Once the sausage is cooked, transfer it with a slotted spoon to a separate plate, and set aside.
Add 1 tablespoon olive oil to the same skillet (or if there is leftover grease from the sausage, I highly recommend using that instead for extra flavor!), and add in the squash. Season with salt and pepper, then sauté for about 10 minutes, stirring occasionally, until tender.
Add the sausage and squash to a large mixing bowl, along with the bread, pecans, cranberries and sage.
In a separate bowl, whisk together the chicken stock and egg until smooth. Pour the egg mixture over the stuffing mixture, and toss until evenly combined.
Spread the stuffing out evenly in a 9 x 5-inch or 2-quart baking dish, and cover loosely with aluminum foil.
Bake (covered) for 40 minutes***. Then remove the foil and bake (uncovered) for 10-15 more minutes, until the top is lightly toasted and golden. (Keep a close eye on the stuffing, though, so that it doesn’t accidentally burn.)
Serve warm, garnished with extra fresh herbs and black pepper if desired.