Preheat an outdoor grill for medium heat and lightly oil the grate.
Grill kielbasa ring on one side for 4 minutes. Transfer to a cutting board, grilled side up.
Cut a slit down the length of the kielbasa, leaving an inch on both ends. Be careful not to cut all the way through as you are just making a pocket. Stuff sauerkraut into the pocket.
Carefully place the kielbasa back on the grill, stuffed side up. Grill for 4 minutes more. Slice into serving portions and serve.