Preheat oven to 400 degrees F. Line a large baking sheet with parchment paper.
Halve each zucchini lengthwise and pat dry. Arrange on baking sheet and fill with cooked sausage. Spoon marinara sauce over top. Sprinkle with mozzarella then top with pepperoni.
Bake for 10 to 12 minutes, or until cheese is melted and bubbly. Sprinkle with fresh parsley or basil. Serve warm.