Combine the brown sugar, paprika, onion powder, salt and chili powder and rub all over the chicken.
Moisten a paper towel with cooking oil. Using long-handled tongs, lightly coat the grill rack with the oil.
Grill the chicken thighs, covered, over medium heat for 5 to 7 minutes on each side, until opaque and cooked through or until a thermometer reads 170°F.
If you don’t have a thermometer, to test for doneness, pierce a thigh with a knife and, if the juice is clear, the thighs are done.
