Halve the potatoes and place them in a bowl. Cover them with water if you cut them ahead of time.
In another bowl, mix olive oil, oregano, garlic, salt, and pepper. Mix well. Drain potatoes well and add them to the oil mixture. Toss with olive oil mixture. Spread the potatoes on a sheet pan. Roast for 30 minutes until potatoes are tender. Sprinkle with cilantro and serve.