Place chicken in a pot with water to cover, and bring to a boil over medium heat. Boil 20 minutes, or until cooked through. Cool, and cut into pieces.
In a slow cooker, stir together chicken, cornbread, bread, eggs, onion, salt, pepper, sage, chicken broth, and chicken soup. Stir until well blended. Dot with margarine.
Cover, and cook on Low for 3 to 4 hours. Remove lid, and fluff with fork. Let rest 15 minutes before serving.