In 10-inch skillet, cook bacon over medium heat 8 to 10 minutes, turning occasionally, until crisp and brown. Remove from skillet; drain on paper towels. Break bacon slices in half.
In small bowl, mash avocado. Stir in dressing.
Spread one side of each bread slice with butter. Place 6 bread slices with buttered sides down; top with turkey, bacon, tomato, cheese and avocado mixture. Top with remaining bread slices, buttered sides up.
In 12-inch skillet, place sandwiches. Cover; cook over medium heat 4 to 5 minutes, turning once, until bread is crisp and cheese is melted.