Heat butter with garlic and salt over moderate heat, stirring, until melted. Transfer to a bowl and cool. Stir in parsley and pepper to taste.
Brush cut sides of bread with half of garlic butter. Grill bread, cut sides down, 5 to 6 inches over glowing coals 2 minutes. Turn bread over and brush with remaining garlic butter. Grill until golden brown, 2 to 3 minutes more.
Herb-garlic butter can be prepared 1 day ahead and chilled, covered. Melt before proceeding.