Preheat Grill For Medium-High Heat. Place Butter, Brown Sugar, Garlic, Lemon Juice, Soy Sauce, And Pepper In A Small Saucepan. Warm Over Medium Heat, Stirring Occasionally, Until Sugar Is Completely Dissolved. Lightly Oil Grill Grate. Brush Fish With Brown Sugar Sauce, And Place On Grill. Cook For 5 Minutes Per Side, Or Until Fish Can Be Easily Flaked With A Fork, Basting With Sauce. Discard Remaining Basting Sauce.