Get the Oven Ready: Preheat your oven to 400°F. Pat the chicken legs dry with a paper towel and set them aside.
Make the Marinade: In a small mixing bowl, zest and juice one of the lemons. This should yield roughly 1 tablespoon of zest and 3 tablespoons of juice. Combine the lemon zest and juice with olive oil, garlic, oregano, salt, and pepper. Stir until blended.
Prepare the Potatoes: Arrange the diced potatoes in a 13 x 9-inch casserole dish. Drizzle half of the prepared marinade over the potatoes, then toss to ensure they are evenly coated.
Marinate the Chicken: Lay the chicken legs on top of the potatoes in the dish. Pour the remaining marinade over the chicken, using your hands or a brush to coat each piece thoroughly.
Add Lemon Slices: Thinly slice the second lemon and arrange the slices on top of the chicken and potatoes for added flavor and visual appeal.
Bake the Dish: Roast in the oven for 50–60 minutes, basting the chicken with pan drippings every 15 minutes. The chicken is fully cooked when its internal temperature reaches 170–175°F using a meat thermometer, and the potatoes are tender.
Optional Adjustments During Cooking: If the chicken skin begins to brown too quickly, cover it loosely with aluminum foil to prevent burning. Remove the foil in the last 10 minutes of roasting if needed for crispiness.
Serve and Enjoy: Remove the dish from the oven, let it rest for a few minutes, and serve warm.