Move oven rack to lowest position. Heat oven to 450°F. Grease large cookie sheet or 12-inch pizza pan. In 10-inch nonstick skillet, heat oil over medium-high heat. Cook chicken in oil 3 minutes, stirring occasionally. Stir in bell pepper and onion. Cook 3 to 4 minutes, stirring occasionally, until chicken is no longer pink in center and vegetables are crisp-tender; remove from heat. Stir in salsa.