Prep: 15 minutes
Marinate: 20 minutes
Bake/Grill: 15 minutes
1/2 cup olive oil
1/4 cup balsamic vinegar
2 tsp. Dijon-style mustard
4 skinless, boneless chicken breast halves
Stir oil, vinegar, and mustard in shallow baking dish or resealable plastic bag. Add chicken and turn to coat. Cover and refrigerate 20 minutes or overnight.
Heat grill to medium. Remove chicken from marinade. Grill chicken 15 minutes or until cooked through, turning chicken over halfway through grilling.