Place bacon in a large, deep skillet. Cook over medium heat, turning frequently, until evenly browned. Drain, crumble and set aside.
In a blender or food processor, combine mayonnaise, milk, garlic powder, and black pepper. Blend until smooth. Season the dressing with salt.
Combine lettuce, tomatoes, bacon and croutons in a large salad bowl.
Toss with dressing and serve immediately.