Place the peppers directly over a gas burner with a high flame. As the pepper skins begin to char, turn them gently with tongs, coloring them evenly all over, about 10 minutes for large bell peppers or 3-5 for the minis. Alternatively, you can place the peppers on a baking tray then roast them in a preheated 475 F oven until the skins are soft and slightly charred, about 20-25 minutes for large bell peppers or 10-15 for the minis.
Transfer the roasted peppers to a bowl and seal tightly with plastic wrap. Allow the peppers to steam until they are cool enough to handle, about 10-15 minutes.
While the peppers are steaming warm the olive oil and sliced garlic together in small saucepan over low heat for 10 minutes. After 10 minutes, turn off the heat and add in the oregano (or basil) and salt. Set aside.
Once the peppers are cool the skin will slide right off easily. Remove skin from the peppers by wiping the peppers with a clean towel. Avoid rinsing under water, as this washes away flavor. A little char left behind is perfectly fine and adds a bit of smokey flavor. Cut away the stems and discard the seeds and any of the white stringy insides.
Transfer the peppers to to a storage container like a large mason jar. Pour the oil and garlic mixture over top. Store in the refrigerator for up to a week.