Preheat oven to 375º. In a small bowl, combine brown sugar, garlic powder, paprika, salt, and pepper. Drizzle oil all over chicken and generously coat with seasoning mixture, shaking off excess. Scatter lemon slices in baking dish then place chicken on top.
Bake until chicken is cooked through, or reads an internal temperature of 165º, about 25 minutes.
Cover chicken loosely with foil and let rest for at least 5 minutes. Garnish with parsley, if using.