Combine tomatoes, basil, mozzarella, 2 tablespoons olive oil and 1/4 teaspoon salt in large bowl. Stir gently.
Heat grill. Cut baguette into 3/4-inch thick slices. Brush with olive oil. Grill bread slices 2 to 3 minutes, turning as needed, until grill marks appear. Serve with tomato-basil mixture for topping. Season with salt and freshly cracked black pepper.