Combine onion powder, white pepper, red pepper, black pepper, and 1/4 teaspoon salt in a small bowl. Trim fat from pork chops. Rub both sides of chops with pepper mixture.
Grill chops on the rack of an uncovered grill directly over medium coals for 25-35 minutes or until no pink remains and juices run clear, turning once. Makes 4 servings.