Method
Heat the oven and season the chicken
Heat the oven to 425°F (220°C). Pat the chicken thighs dry. Mix 2 tbsp olive oil, garlic, 1½ tsp paprika, oregano, lemon zest, lemon juice, ½ tsp salt, and ¼ tsp black pepper. Rub the mixture over the chicken, including beneath the skin where accessible. Keep the thighs refrigerated if preparing ahead.
Give the potatoes a head start
Toss the potatoes with the remaining 1 tbsp olive oil, ½ tsp paprika, ½ tsp salt, and ¼ tsp pepper. Spread in a large roasting pan or rimmed sheet pan in a single layer. Roast for 15 minutes.
Add the chicken and vegetables
Turn the potatoes and add the onion and red pepper, tossing them in the oil in the pan. Arrange the thighs skin-side up among the vegetables. Leave space around the pieces; use two pans if needed.
Roast until cooked through
Roast for another 40–50 minutes, turning the vegetables once while keeping the chicken skin-side up. The potatoes should be tender and browned. Check the chicken with a thermometer in the thickest part, avoiding the bone; it must reach at least 165°F. If the chicken finishes before the potatoes, transfer it to a plate and continue roasting the vegetables until tender. If the skin darkens too quickly, loosely shield the chicken with foil.
Rest and serve
Rest the chicken for 5 minutes. Toss the vegetables in the pan juices, taste for seasoning, and sprinkle everything with parsley. Serve with lemon wedges.