Heat oven to 350°. Lightly grease a 9-inch square baking dish or spray with nonstick cooking spray.
In a large saucepan, heat butter over medium low heat; add green onions and chicken. Sauté the onions and chicken in the saucepan, stirring constantly, for about 2 minutes. Add vegetables, pepper, prepared shells and cheese, soup, and cheese. Stir and heat through. Transfer to the prepared baking dish. Bake for 25 minutes, or until browned and bubbly.
Calories per serving: 377
Fat per serving: 13.0g