When cooking Chicken Breast in the oven preheat the oven to 400 F and then place the thawed out chicken breast in the oven and let it cook for 30 to 45 minutes.
Check the chicken after 30 minutes and see if there's any red parts or blood in the chicken and if there is then the chicken breasts need to cook longer.
I find that when I bake chicken breasts in the oven it takes 45 minutes to fully cook.
I use a meat thermometer and stick the probe in the fattest part of the chicken breast and if the internal temperature is 165F or 180 F or higher then the chicken breast is fully cooked.