Barbecued Hamburger Mix

4 pounds ground beef
2 medium onions, chopped (about 1 cup)
1 bottle (14 ounces) catsup
1 cup water
1/2 cup chopped celery
1/4 cup lemon juice
2 tablespoons brown sugar
1 tablespoon Worcestershire sauce
1 tablespoon salt
2 teaspoons vinegar
1/2 teaspoon dry mustard

In Dutch oven or roasting pan, cook and stir ground beef and onion until meat is brown and onion is tender. Drain off fat. Stir in remaining ingredients; heat to boiling, stirring frequently. Simmer covered 30 minutes