Heat oil in stockpot over medium heat until hot. Place chuck roast in stockpot; brown evenly. Pour off drippings; season with salt and pepper, as desired.
Add beer, peppers, and 2 tablespoons adobo sauce to stockpot; bring to a boil. Reduce heat; cover tightly and simmer 2 hours and 15 minutes to 2 hours and 30 minutes or until pot roast is fork-tender.
Combine coleslaw and remaining 1 teaspoon adobo sauce. Refrigerate until ready to use.
Remove roast; cool slightly. Skim fat from cooking liquid; bring to boil. Reduce to medium and cook 10 to 12 minutes or until reduced to 1-1/2 cups. Meanwhile, trim and discard excess fat from cooked roast. Shred roast with 2 forks. Return beef to reserved liquid; cook over medium heat until heated through.
Serve beef in tortillas; top with coleslaw mixture and toppings as desired.
