In a shallow 9 X 13 inch glass dish, prepare all of the marinade ingredients. Remember, if you have more than 2 8 oz tuna steaks, you might need to adjust the ingredients to marinate.
Marinate both sides (dredge steaks and get marinade on both sides).
Let sit in refrigerator for 30 minutes before grilling. Note: Soy sauce will overpower tuna if you marinate for too long!
Light the grill while tuna is marinating. Once coals are white (30 minutes) spread them and clean the grill, then wipe with oil so steaks don't stick.
Grill for 4 minutes or less per side for 1 inch steaks, depending on how you like them. Steaks should be firm with pink in the middle. If you prefer steaks to be more rare, grilling time should be 2 1/2 minutes on each side.