Pat the turkey breast thoroughly dry with paper towels. This helps the seasoning adhere better and creates a nicer texture.
In a small bowl, mix together the olive oil, salt, black pepper, garlic powder, onion powder, dried thyme, and dried rosemary to create a seasoning rub.
Rub the seasoning mixture generously all over the turkey breast, ensuring it's evenly coated.
Place the seasoned turkey breast into the slow cooker. In a separate small bowl, whisk together the chicken broth and melted butter. Pour this liquid mixture over the turkey breast in the slow cooker.
Cover the slow cooker and cook on LOW for 3.5 to 4 hours, or on HIGH for 2 to 2.5 hours. The turkey is done when an instant-read meat thermometer inserted into the thickest part of the breast registers 165°F (74°C). Cooking time may vary slightly based on the size of your turkey breast and your slow cooker.
Carefully remove the cooked turkey breast from the slow cooker and transfer it to a clean cutting board. Tent it loosely with aluminum foil and let it rest for at least 15 minutes before slicing. Resting allows the juices to redistribute, ensuring a moist and tender result.
Optional Gravy: If desired, carefully skim off any excess fat from the cooking liquid remaining in the slow cooker. In a small bowl, whisk together the cornstarch and cold water to form a smooth slurry. Stir the cornstarch slurry into the cooking liquid in the slow cooker. Turn the slow cooker to HIGH (or transfer liquid to a saucepan and bring to a simmer on the stove). Cook for 15-20 minutes, stirring occasionally, until the gravy has thickened to your desired consistency. Season the gravy with additional salt and pepper to taste.
Slice the rested turkey breast against the grain into desired thickness. Serve immediately with the homemade gravy and your favorite side dishes.
Notes
For an extra boost of flavor, you can add a few sprigs of fresh rosemary or thyme to the slow cooker along with the turkey. Do not overcook the turkey, as this is the most common reason for dry turkey breast. Always use a meat thermometer to ensure it reaches 165°F (74°C) but not much higher. Leftover turkey can be stored in an airtight container in the refrigerator for up to 3-4 days. It's delicious in sandwiches, salads, or reheated gently with a splash of broth.
Keyword Holiday Meal, Moist Turkey, slow cooker, Thanksgiving, The Juiciest Slow Cooker Turkey Breast, Turkey Breast