1Heat gas or charcoal grill. Brush both sides of chicken with oil; sprinkle with taco seasoning mix.
2Place chicken on grill. Cover grill; cook over medium heat 15 to 20 minutes, turning once and topping each chicken breast with cheese during last minute of cooking time, until juice of chicken is clear when center of thickest part is cut (170°F). Serve chicken topped with salsa.