Poke holes in flat irons on both sides and season with seasoned salt, as desired.
Place steaks in a non-reactive container, such as a glass baking dish.
Combine remaining ingredients and pour over steak.
Marinate steak in the refrigerator for at least 4 hours, or overnight.
Preheat grill to medium heat and grill steak for 15-20 minutes, or until internal temperature reaches 145° F.
Total Time: 30 minutes
368 calories; 16 g fat; 4 g saturated fat; 1087 mg sodium; 95 mg cholesterol; 9 g carbohydrate; 0 g fiber; 30 g protein