Set grill to high heat.
Brush one side of each bread slice with oil.
Be sure to rub cut sides of garlic over oil.
Spread 1/2 tsp of Dijon mustard on each of 4 bread slices, oil side down.
Top each bread slice with 1 oz cheese, 1/3 cup greens, avocado and 2 tomato slices.
Top each with remaining 4 bread slices, oil side up.
Place sandwiches on grill rack coated with olive oil.
Grill 2 minutes on each side or until lightly toasted and cheese melts.