Oven-baking turkey breast: If internal temperature of the thickest part of the turkey breast rise too much above 165℉, turkey will be dry and no longer juicy. The ideal scenario is to get turkey out of the oven as soon as it reaches 165℉. Cook time for turkey breast varies significantly depending on the size of turkey, initial internal temperature of turkey etc. As a point of reference, my 5 lbs bone-in, skin-on turkey breast took about 2 hours to cook.