Spread one side of sandwiches with honey Dijon dressing, and top with baby spinach leaves. Next, layer turkey breast and red onion over the spinach.

On the other half of the sandwich, place the avocado slices. Season to taste with salt and pepper. Sprinkle goat cheese over avocado slices. Close sandwiches.

Preheat a panini press according to manufacturer's directions. Spray panini press with cooking spray. Place sandwiches into the press and close. Cook until the bread is toasted and crisp, with golden brown grill marks and the cheese begins to melt, 5 to 8 minutes.