Heat oven to 350*F. Combine reserved pineapple juice, butter, brown sugar, cornstarch, vinegar, soy sauce and ginger in 1-quart saucepan. Cook over medium heat, stirring occasionally, until mixture is thickened and bubbly (4 to 6 minutes). Boil, stirring constantly, 1 minute.
Place sauce, pineapple chunks, bell peppers and meatballs into ungreased 2-quart casserole; stir gently to coat. Cover; bake for 25 to 30 minutes or until meatballs are heated through. Serve in chafing dish with toothpicks or keep warm in slow cooker.