1Place meatballs in 3- to 4-quart slow cooker. Place bell peppers in blender; cover and blend until smooth. Add cheese and Italian dressing; cover and blend until mixed. Add marinara sauce; pulse until just blended. Pour sauce over meatballs.
2Cover and cook on Low heat setting 6 to 7 hours.
3Stir before serving. Meatballs will hold on Low heat setting up to 2 hours; stir occasionally.