In a large bowl, combine turkey, Hatch chiles, onion, cumin, chile pepper if using, salt, and ground black pepper. Mix thoroughly.
If mixture seems too wet, add breadcrumbs, a little at a time, until you can form a patty that does not fall apart.
Divide mixture into four and shape into patties. Set aside on a plate.
When ready to cook, prepare a grill for direct medium heat and grill 6-10 minutes on each side, or until a thermometer inserted in the center reads 165°F.
If using cheese, add in the last minute or two of cooking to melt. Serve with your favorite toppings.
Notes
Burgers can be baked in the oven at 375°F for 20-25 minutes, flipping halfway though.