Step 1

Preheat oven to 350 degrees F. Heat oil in a medium saucepan over medium-high heat. Add onion and garlic; cook, stirring occasionally, until the onion is translucent, 4 to 5 minutes. Add quinoa; cook, stirring occasionally, for 30 seconds. Add water; increase heat to high and bring to a boil. Reduce heat to medium; cover and cook for 15 minutes. Remove from heat; let stand, covered, for 5 minutes. Stir in chicken, marinara, Parmesan and 1/2 cup basil.

Step 2

Trim top 1/2 inch from peppers; remove seeds and membranes. Arrange the peppers, cut-sides up, in an 8-inch-square glass baking dish. Cover with plastic wrap; microwave on High for 3 minutes. Remove plastic wrap. Spoon the quinoa mixture evenly into the pepper halves (about 1 1/4 cups each).

Step 3

Bake the stuffed peppers until they are softened, about 15 minutes. Sprinkle evenly with mozzarella. Continue baking until the cheese is melted, 5 to 7 minutes. Sprinkle evenly with the remaining 1/4 cup basil.