Place flank steak in a heavy-duty zip-top plastic bag; add Southwestern Marinade. Seal and chill 8 hours, turning occasionally.
Remove steak from marinade, discarding marinade.
Grill steak, covered with grill lid, over medium-high heat (350° to 400°) 8 to 10 minutes on each side or to desired degree of doneness. Cut steak diagonally across the grain into thin strips. Serve with Apple-Bourbon Sauce and Roasted Vegetables. Garnish, if desired.