BBQ Pot Roast

1 pot roast (about 4 pounds), such as bottom round or chuck
1 teaspoon vegetable oil
1 cup bottled barbecue sauce
1/2 cup cider vinegar
1/2 cup chicken or beef broth
1/4 cup packed brown sugar
1 tablespoon bottled mustard
1 tablespoon Worcestershire sauce
1 tablespoon chili powder
1 large onion (1/2 pound), chopped
2 large cloves garlic, crushed
1 1/2 teaspoons dried thyme
12 rolls

Heat oven to 300 degrees F.

Brown meat well in oil in large ovenproof Dutch oven, 15 minutes. Add sauce, vinegar, broth, sugar, mustard, Worcestershire, chili powder, onion, garlic and thyme to pot. Bring to boiling. Place in oven and bake, covered, for 3 to 4 hours, turning meat every hour, until fork-tender. Let stand at least 30 minutes in pan. Remove meat from pot and shred with two forks. Skim fat from sauce and boil until reduced. Serve beef with sauce on toasted rolls.