In a small mixing bowl, combine the cumin, chili powder, salt, pepper, crushed red pepper and cinnamon, stirring well to mix.
Place flank steak in the bottom of a baking dish, and brush both sides of the steak with the oil.
Sprinkle both sides of the steak with the seasoning mixture, and set aside.
Coat grill rack with cooking spray. Prepare the grill to medium-high heat.
Grill steak for about 6 minutes on each side, or to desired doneness. Remove steak to cutting board, and let rest about 10 minutes. Slice steak diagonally across the grain before serving.