Red Onion, Garlic, Mint - Stuffed Grilled Zucchini

4 medium zucchini

5 teaspoons olive oil, divided

2 tablespoons finely chopped red onion

1/4 teaspoon minced garlic

1/2 cup dry bread crumbs

1/2 cup shredded part-skim mozzarella cheese

1 tablespoon minced fresh mint

1/2 teaspoon salt

3 tablespoons grated Parmesan cheese

Cut zucchini in half lengthwise; scoop out pulp, leaving 1/4-in. shells. Brush with 2 teaspoons oil; set aside. Chop pulp. In a large skillet, sauté pulp and onion in remaining oil. Add garlic; cook 1 minute longer. Add bread crumbs; cook and stir until golden brown, about 2 minutes. Remove from the heat. Stir in the mozzarella cheese, mint and salt. Spoon into zucchini shells. Sprinkle with Parmesan cheese. Grill, covered, over medium heat until zucchini is tender, 8-10 minutes