In a food processor, blend together the beer, chipotle peppers, oregano, cumin, and brown sugar until smooth.
Place the chicken in a large bowl or ziploc bag and pour ½ of marinade over top. Cover and refrigerate 4-5 hours.
Preheat grill to high. Turn heat off on one side of the grill. Place chicken thighs on the half of grill that you turned off the heat. (cooking over indirect heat)
Grill chicken for 5-7 minutes on each side, until chicken is no longer pink.
Remove chicken from grill and let sit 10 minutes. Drizzle with reserved marinade for extra boost of flavor.
Serve as as a warm salad with your favorite ingredients or wrap in a tortilla with your favorite taco toppings.