Heat the oven to 375°F. Lightly grease a baking dish with the olive oil.
In a large bowl, combine the ground turkey, crushed stuffing mix, egg, milk, Parmesan, Italian seasoning, garlic powder, black pepper, and 1/4 cup of the marinara sauce. Mix gently until just combined.
Shape the mixture into a loaf in the prepared baking dish. Spread another 1/2 cup marinara over the top.
Bake for 40 to 50 minutes, until the center reaches 165°F. Let the meatloaf rest for 5 minutes before slicing.
While the meatloaf bakes, cook the spaghetti according to the package directions. Drain it, then toss it with the remaining 1/4 cup marinara sauce.
Serve slices of meatloaf alongside the spaghetti.