Preheat the oven to 450°F. Line a rimmed baking sheet with high-heat-resistant parchment paper or foil.
Cut the bell peppers into quarters, then remove the seeds and membranes.
Place the peppers on the prepared baking sheet. Drizzle them with olive oil and use your hands to coat them well.
Sprinkle the peppers with salt, pepper, garlic powder, oregano, and red pepper flakes.
Roast until tender and charred in spots, about 20 minutes. Serve immediately.
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Notes
Different pepper colors make for a pretty presentation, enough to serve this dish to guests. There are also subtle flavor differences between different-colored bell peppers, making for a more interesting dish all around, not just visually.
There's no need to turn the peppers midway through baking.
There's no need to peel the peppers.
These peppers keep well in a sealed container in the fridge for 3-4 days. To serve the leftovers, gently reheat them in the microwave at 50% power or serve them cold like antipasti.