For best results, you should thaw frozen chicken breasts before cooking them, especially for this recipe for marinated grilled chicken breasts. Leave them in the refrigerator overnight to thaw, or defrost them the same day by using the cold water bath method. Place the chicken breasts in an airtight sealed plastic bag in a bowl of cold water. Change the cold water every 30 minutes so it's fresh (this is crucial as you do not want the water warming up at all). A chicken breast takes about 1 hour to thaw this way.