In a small bowl, combine the marmalade, cranberry sauce and grated orange peel. Divide mixture in half, pouring half over the turkey. Refrigerate the remaining half of the sauce for serving.
Cook in the slow cooker on high for one hour, then switch to low for 5-6 hours until turkey is cooked through. Alternatively, you can cook on low for 8-1/2 hours.
Remove turkey breast from slow cooker and allow to rest for 15 minutes.
Heat remaining cranberry sauce mixture in microwave for 30 seconds or until hot, and serve over sliced turkey breast. If you do not have a microwave, you can heat the sauce over low heat on the stove, stirring regularly, while the turkey rests.
You can use spiced orange marmalade if available to give it a holiday spice flavor too. Or adding a pinch of cinnamon, cloves and nutmeg to regular marmalade, mixed well, will add similar flavors to this dish.