1 (3-5 lb.) round bone beef roast
2/3 c. vinegar
1 (32 oz.) bottle ketchup
1 med. onion, minced
1 tbsp. brown sugar

Cover, simmer all day (about 8 hours), in oven at 300 degrees. As roast becomes tender, pull apart with a fork. Repeat until roast is completely shredded. Serve on sandwich rolls.