I have several suggestions. The first one is check your oven temperature with a thermometer to make sure it's the correct temperature. Second, the length of time you cook the breasts depends on how big they are, so you may have to adjust the time. Third, it's very important to wrap beef, chicken or pork with aluminin foil and let it rest for 15 minutes after cooking, to let the juice get back into the meat. I hope that helps!