Roast Chicken with Acorn Squash and Radicchio Salad

Preheat oven to 450 degrees with rack in upper third. On a rimmed baking sheet, toss squash with 1 tablespoon oil. Rub 1 tablespoon olive oil on chicken. Tie legs together and tuck wing tips beneath body and add to sheet. Season squash and chicken with salt and pepper. Roast until chicken is cooked through, 40 to 50 minutes. Transfer chicken to a cutting board and let rest 10 minutes.

Meanwhile, whisk together red wine vinegar, mustard, and remaining 4 tablespoons olive oil. Season with salt and pepper. Arrange radicchio and squash on a platter, drizzle with dressing, and sprinkle with parsley. Serve salad with chicken.