Preheat broiler. Place a baking sheet in oven while broiler preheats.
Combine flour, salt, and pepper in a shallow dish. Place breadcrumbs in a shallow dish. Place egg whites in a small bowl, and whisk until foamy.
Halve avocados, remove pits, and cut each half into 6 wedges. Pull off peels.
Dredge avocado wedges in flour, dip in egg white, and then dredge in breadcrumbs. Remove baking sheet from oven; coat with cooking spray. Place avocado slices on baking sheet; coat avocados with cooking spray.
Broil 5 minutes or until brown on top. Turn and broil 2 more minutes. Remove and serve with lemon wedges.