Prepare the marinade. In a large bowl, whisk together the yogurt, olive oil, lemon juice, minced garlic, onion powder, ground coriander, cumin, turmeric, smoked paprika, salt, and black pepper. Stir in the harissa paste if using.
Marinate the chicken. Add the chicken leg quarters to the bowl and turn to coat them well in the marinade. Cover and refrigerate for at least 2 hours, or overnight for deeper flavor.
Preheat the oven. When ready to cook, preheat the oven to 400°F.
Arrange the chicken. Transfer the marinated chicken to a large baking dish or roasting pan, skin-side up. Spoon any remaining marinade over the chicken and drizzle lightly with olive oil.
Bake. Cover the dish tightly with foil and bake for 35–40 minutes, allowing the chicken to cook gently and stay tender and juicy. Remove the foil and continue baking for 20–25 minutes, or until the chicken is golden and cooked through and the internal temperature reaches 165°F. For extra color and crisp skin, broil for the last 2–3 minutes if desired.
Rest and Serve. Let the chicken rest for about 5 minutes before serving. Spoon some of the flavorful pan juices over the chicken.