Mix beef, chilies, cilantro, chili powder, salt and red pepper. Shape mixture into 4 patties, about 1/2 inch thick.
Spray 10-inch nonstick skillet with cooking spray; heat over medium-high heat. Cook onion in skillet 1 to 2 minutes, stirring occasionally, just until tender. Remove from skillet.
Add beef patties to skillet. Cook 10 to 12 minutes, turning once, until no longer pink in center and juice is clear. Top patties with onions, avocado and cheese. Cover and heat until cheese is melted.