In a small bowl, combine 1/3 cup of the olive oil and half the garlic. Let stand at room temperature for 30 minutes.

Place the red onion slices in a large salad bowl and coat with the balsamic vinegar. Set aside for 30 minutes or longer to soften.

Prepare the grill. Brush the bread slices generously on both sides with the garlic oil. When the grill is ready, place the bread on the grill and toast, turning the slices once or twice, until they are crisp and golden brown. Cool and with a serrated knife, cut the slices into 1-inch cubes.

Core the tomatoes and cut them into large cubes. Place the tomatoes in a medium bowl along with their juices, the remaining garlic, 3 tablespoons olive oil, salt and pepper. Let stand for at least 15 minutes, stirring once or twice.

Just before serving, add the tomato mixture and bread cubes to the onions in the salad bowl and toss gently. Add the blue cheese and toss once more. Serve right away.