First, it’s important to know that the cooking time will depend on the size of your chicken breast and also on the power of your oven as some ovens have slight heat differences. But according to USDA, a 4-oz. chicken breast should be bake at 350°F (177˚C) for 25 minutes or 30 minutes. But if the chicken breast is smaller then 4oz, bake it for about 20 minutes. Or it can be bake at 425˚F for about 18-20 minutes.