Mix ground beef with chilies, onion, garlic, salt and pepper. Blend well, but gently.
Form into 6 patties. Grill, uncovered, about 4" from medium coals or other heat source until cooked to internal temperature of 160°F (about 12-15 minutes).
Turn once halfway through cooking time. One minute before burgers are done, add cheese and continue to cook until cheese is melted.
Top burgers with lettuce and tomato or your choice of toppings.