Heating the oil before adding the potatoes makes them crisp on the outside, soft on the inside.
Heat oven to 425 degrees. Peel potatoes into egg shapes with a paring knife; place them in water as you work. Drain; dry potatoes. Toss with lemon juice, oregano, salt, and pepper.
Pour oil into a shallow baking pan; place pan in oven until oil is hot, 3 to 5 minutes.
Add potatoes to pan; roast 10 minutes, then turn potatoes. Continue roasting until potatoes are brown, crisp, and tender, turning twice, about 30 minutes.