Preheat the oven to 350°F. Butter a 2-quart casserole pan or 9" x 13" pan.
Place the bread cubes into a large bowl, and set aside.
Heat the vegetable oil in a large frying pan over medium-high heat.
Brown the sausage meat, breaking it up with a spoon until it's completely cooked through, about 8 to 10 minutes.
Transfer the cooked sausage to the bowl with the bread cubes, leaving the hot fat in the pan. Toss the bread with the sausage until the two are evenly incorporated.
Return the pan to the heat and add the onion, celery, and apple. Cook until the onions are translucent and everything has softened.
Transfer the vegetable mixture to the bread cubes/sausage, stirring to incorporate.
Stir in the butter, stock, salt, pepper, and parsley, mixing thoroughly.
Stir in the beaten eggs. Transfer the stuffing to the prepared pan.
Bake the stuffing for 50 to 60 minutes, until the top is crunchy and sizzling.
Remove the stuffing from the oven. Allow it to cool for 5 to 10 minutes before serving.