In a small bowl, combine blue cheese, cream cheese, scallions and pepper; mix well. Butter one side of each slice of bread. Spread the cheese mixture on the non-buttered side of 4 slices of bread. Cut bacon slices in half; place 2 halves on top of each cheese-topped slice. Cover with remaining 4 slices of bread, buttered side out.
Place sandwiches on an electric griddle heated to 275° F, or in a preheated skillet over medium heat. Cook 4 to 5 minutes per side, or until bread is golden brown, and cheese is melted.