Preheat grill.
In a large bowl mix together the olive oil, lemon juice, oregano, salt and pepper, and garlic.
Whisk until well blended.
Add the cobia fillets and marinate in the refrigerator for at least 30 minutes.
Roll the fresh mint to use like a basting brush.
Place the fillets on the grill.
Use the fresh mint as a brush and baste the fish with the marinade.
Cook the fillets about 4-5 minutes on each side.
Serve immediately.