If you're not inclined to cut your potatoes into perfect ovals, simply peel and quarter them. More Potato Dishes
Using a paring knife, peel each potato quarter lengthwise and shape it into a long oval.
Heat the olive oil in a large skillet. Add the potatoes and cook over moderate heat until browned on all sides, about 15 minutes. Add the butter and cook over moderately low heat, turning often, until tender, about 10 minutes longer. Season the potatoes with salt and pepper. Using a slotted spoon, transfer the sautéed potatoes to a large bowl and serve at once.
The sautéed potatoes can stand at room temperature for up to 8 hours. Rewarm in a 400° oven.