Working with one sandwich at a time, or assembling all four simultaneously, arrange 4 ounces turkey meat on the bottom half of a croissant. Top each with 2 slices of bacon, a lettuce leaf, tomato slices, and avocado slices.
Season the tomato and avocado slices to taste with salt and pepper. Spread a layer of mayonnaise on the top half of each croissant and place on top of the sandwich. Serve immediately!