Preheat oven to 350 degrees F. Coat the bottom of a glass baking dish with olive oil.
Wash and peel the sweet potatoes. Cut them into chunks.
Place the cut sweet potatoes in the baking dish and toss them until they are coated with the olive oil. Spread them out into a single layer. Sprinkle with oregano, salt and pepper.
Bake in the preheated oven for 60 minutes or until soft.