Beef Stroganoff (Slow Cooker)

1 1/2 lbs stew meat, cut up
1 chopped onion
2 cans cream of mushroom soup
2 TBS ketchup
2 tsp worchestershire sauce
1 tsp pepper
1 pint sour cream

Combine all but sour cream in slow cooker. Cook low 8-10 hours. Mix in sour cream and cook 10 min. more. Serve over egg noodles or rice.