Spray 13x9-inch (3-quart) glass baking dish with cooking spray. In 12-inch skillet, cook sausage over medium heat 5 to 7 minutes, stirring occasionally, until sausage begins to brown; drain if necessary. Add onion; cook 2 to 3 minutes or until slightly softened. Add both bell peppers; cook and stir 1 minute. Add garlic; cook and stir 30 seconds or until softened.