A 5-pound turkey breast takes approximately two hours to cook at 325 F in a regular oven. A stuffed turkey breast will take up to two hours and 45 minutes. Unstuffed turkey breasts should be cooked to an internal temperature of 170 F, while stuffed breasts should measure 165 F.
To determine the internal temperature, insert the thermometer into the thickest part of the breast meat, avoiding contact with any bones, to ensure an accurate reading. After removing it from the oven, allow the cooked turkey breast to stand for 10 to 20 minutes, covered with foil. The exact cooking time may vary when using an oven roasting bag or cooking the turkey in a convection oven.