Heat a grill (or grill pan) to medium-high heat (350 to 450 degrees F).
Wash and fully dry the peppers.
Add the oil, garlic powder, salt, and cumin to a mixing bowl and stir until combined. Add the peppers and toss until they are fully coated with oil.
Thread the peppers onto metal or bamboo skewers. Place the skewers on the grill and cook for 3 to 4 minutes till grill lines have formed, then flip and grill for an additional 3 to 4 minutes.
Remove from the grill and top with an optional squeeze of lime juice. Serve immediately.