Place flank steak in a large baggie (use a freezer bag) and pound it to about 1/2' thick. Place 1/4 cup of Stubb’s Beef Marinade over steak (be sure that the steak is completely covered). Place in refrigerator and marinate for 1 hour or overnight.
Heat grill to medium heat, place flank steak on grill, discard leftover marinade. Cook steak for about 5 minutes per side. (Don't overcook the flank steak or it can become tough.)
Cover the flank steak with aluminum foil and let it rest for 10 minutes. Thinly cut the steak against the grain.
Eat plain, or add to tacos, and/or top with your favorite Stubb’s Bar-B-Q Sauce.