Combine potatoes and enough water to cover by 1 inch in a large saucepan; bring to a boil. Reduce heat and simmer until tender, about 12 minutes; drain and return the potatoes to the pan.
Use a potato masher to coarsely mash the potatoes.
In a small bowl, whisk together the oil, zest, juice, salt and pepper. Drizzle onto the potatoes and use a wooden spoon to mix it in.