Thaw fish, if frozen. Rinse; pat dry with paper towels. Cut in 4 serving-size pieces. Brush with oil; sprinkle with 1/4 teaspoon salt and 1/8 teaspoon black pepper. Measure thickness of fish.
For charcoal grill, place fish on greased rack of uncovered grill directly over medium coals. Grill 4 to 6 minutes per 1/2-inch thickness of fish or until fish flakes easily when tested with fork; carefully turn once halfway through grilling. (For gas grill, preheat. Reduce heat to medium. Place fish on greased grill rack over heat; cover. Grill as above.)
In bowl combine parsley, basil, lemon peel, and rosemary. Sprinkle on fish. Makes 4 servings.