In 10-inch skillet, cook beef, sausage and onion over medium-high heat 5 to 7 minutes, stirring occasionally, until beef and sausage are thoroughly cooked; drain.
Spray 3- to 4-quart slow cooker with cooking spray. In cooker, mix beef mixture and remaining ingredients except sour cream and green onions.
Cover; cook on Low heat setting 7 to 8 hours. Top individual servings with sour cream and green onions.