Begin by washing and trimming the radishes. Cut them in half or quarters, depending on their size, to ensure even cooking.
In a mixing bowl, combine the radishes, olive oil, minced garlic, salt, black pepper, and oregano (if using). Toss everything together until the radishes are evenly coated.
Preheat your air fryer to 400°F (200°C) for about 3 minutes.
Place the seasoned radishes in the air fryer basket in a single layer. You may need to cook them in batches if your air fryer is small.
Cook the radishes for 12-15 minutes, shaking the basket halfway through. They should become tender and crispy.
In the final 2 minutes of cooking time, sprinkle the grated Parmesan cheese over the radishes, allowing it to melt and form a golden crust.
Once done, remove the radishes from the air fryer and transfer them to a serving dish. Garnish with chopped parsley if desired.