- Preheat the oven to 400 degrees F. Coat a large rectangular baking dish with cooking spray.
- Cut the zucchini in half lengthwise, then trim off the stem ends. Use a spoon to carefully scoop the flesh out of the zucchinis.
- Sprinkle the Italian seasoning, salt and pepper over the zucchini shells. Arrange the zucchini in the baking dish.
- Heat the olive oil in a large pan over medium high heat. Add the sausage (out of casing) and cook for 4-5 minutes, breaking up the meat with a spatula.
- Add the onion and cook for an additional 4 minutes or until onion is softened. Add the garlic and cook for 30 seconds.
- Season the sausage and vegetable mixture with salt and pepper.
- Pour the marinara sauce into the pan and bring to a simmer; cook for 5 minutes.
- Spoon the meat mixture evenly into the zucchini shells, then top with the shredded cheese.
- Bake for 25 minutes, or until zucchini is tender and cheese is melted and golden brown.
Sprinkle with parsley, then serve.