For a charcoal grill, grill bread over medium coals for 2 to 3 minutes per side or or until lightly toasted. (For a gas grill, preheat grill. Reduce heat to medium. Place bread on grill rack; grill as above.) Remove bread slices from grill.
Rub one side of each toast with garlic; brush with olive oil. On each slice of toast layer 1/2 tablespoon cheese, 1 tablespoon arugula, and another 1/2 tablespoon cheese.
Return bruschetta to grill; grill for 6 to 7 minutes more or until cheese is melted. Top each bruschetta with 1 teaspoon pesto; serve immediately.