Begin by cutting the Zucchini lengthwise, then scooping out the pulp and set aside. I found this was easiest using a tablespoon size measuring spoon. Be sure to discard any pulp with seeds.
In a large skillet on medium heat begin cooking the sausage and the onion. Once the sausage is well cooked, drain it and return to the skillet. At this point add in the peppers, garlic, and the zucchini pulp. I let this simmer for 5-10 minutes until soft and well mixed.
Fill each zucchini half with the mixture then top with Parmesan cheese.
Place these in a greased 9x13 casserole dish and bake for 15 minutes.
To make these party size, I simply cut them in fourths.