Preheat the oven to 375 degrees F. Lightly grease a baking dish that will hold the peppers upright.

Slice the tops off each orange bell pepper and set them aside. Remove the seeds and membranes. Use a small knife to carve simple jack-o'-lantern faces into the sides of the peppers.

Heat the olive oil in a large skillet over medium heat. Add the Italian sausage and cook, breaking it up with a spoon, until browned.

Add the chopped onion and minced garlic to the skillet. Cook for 3 to 4 minutes until the onion softens.

Stir in the cooked white rice, marinara sauce, Italian seasoning, salt, and black pepper. Mix well and cook for 2 minutes until heated through. Remove from heat and stir in half the shredded mozzarella cheese.

Spoon the filling evenly into the carved peppers. Place the peppers in the prepared baking dish and sprinkle the remaining cheese on top. Replace the pepper tops if desired.

Bake for 25 to 30 minutes until the peppers are tender and the cheese is melted and lightly browned.