Parmesan and breadcrumbs combine for a crispy chicken topping without having to go through the full dredging process. While your oven's on, roast some potatoes to serve alongside for a balanced, filling meal.
Preheat oven to 425°F.
Stir Parmesan, 1 tablespoon oil, panko, lemon zest, dried thyme, 1/8 teaspoon salt and 1/4 teaspoon pepper in a small bowl.
Toss Brussels sprouts, onion and garlic with 2 tablespoons oil and the remaining 1/2 teaspoon salt and 1/4 teaspoon pepper on a large rimmed baking sheet. Spread out evenly. Add chicken and lemon wedges to the pan. Brush both sides of the chicken with the remaining 1 tablespoon oil. Top the chicken with the Parmesan mixture, gently pressing to adhere.
Roast, turning the pan from front to back and stirring the sprouts halfway, until an instant-read thermometer inserted in the thickest part of a thigh registers 165°F and the sprouts are tender and browned in spots, about 18 minutes. Garnish with fresh thyme and serve with the lemon wedges, if desired.