Put the cover on the slow cooker and cook on low for 3-5 hours. Use an instant-read meat thermometer to check that the thickest part has reached 165 degrees F internally.
Once the meat is cooked, remove the turkey from the slow cooker and set it aside to rest for 10 minutes before slicing.
Meanwhile, whisk the second brown gravy envelope into the slow cooker with the remaining liquid to make the gravy.
2 envelopes brown gravy mix
Slice and serve with the thick gravy.
Notes
Always verify the internal temperature of the meat has reached 165 degrees F before serving.
If your turkey breast is frozen, thaw it before cooking.
You can use a bone-in turkey breast, but increase the cooking time to 4-6 hours on low.
Use a crockpot liner to make cleanup fast and easy. This is especially useful when making a big holiday dinner with many dishes!
To crisp the outside of the meat, put the cooked turkey on a baking sheet and place it under the broiler for 2-3 minutes.