Preheat a charcoal or gas grill for direct cooking over medium-high heat. Add butter to a microwave-safe bowl. Microwave on high for 30 seconds or until melted. Stir in garlic. Brush garlic butter on both sides of each bread slice. Grill for 3 minutes or until crisp and golden, turning once. Cool on a rack.
Thread tomatoes on skewers; brush with olive oil. Grill for 2 to 3 minutes or until tomatoes are slightly charred, turning once.
Top bread with mozzarella, pesto and tomatoes. If desired, garnish with parsley.