Slow Cooker Instructions: Heat oil in a medium skillet over medium-high heat. Once hot, add onion and cook until softened, about 4 to 5 minutes, stirring occasionally. Stir in garlic and cook for about 30 seconds to 1 minute until fragrant. Add this mixture to the slow cooker insert with remaining ingredients, except for the turkey. Cook on High for 3 hours or Low for 6 hours. In the last 30 minutes of cooking on High heat (or last hour for Low heat), stir in turkey, cover, and continue cooking. Serve!