Combine all orange marinade ingredients into a medium size bowl. Stir to combine.
Place the flank steak into a plastic zipper bag or bowl. Add the marinade to the container and coat steak completely. Remove air from bag and zip closed or cover bowl with a tight fitting lid, plastic wrap or foil. Place in the refrigerator for at least 2 hours.
After about 1 hour and 45 min, start your grill or bbq and let it heat up to 350 degrees.
Remove the flank steak from the fridge, place the steaks onto the heated grill. Cook 15-20 minutes per side. (Less if you like it rare)
Flip the steaks and continue cooking for another 15-20 minutes. You can cut into the steak to see if it is done to your liking. The internal temperature should be at least 130-135 degrees for medium rare and 145 degrees for medium.
Remove the steak from the grill and wrap in foil. Let it rest for 7-10 minutes.