Preheat oven to 425°F. Line sheet pan with foil, if desired.
Whisk oil, vinegar, salt, garlic powder, black pepper and red pepper flakes in small bowl until well blended. Combine chicken, sausage and onions on prepared sheet pan. Drizzle with oil mixture, toss until well coated. Spread meat and onions in single layer (chicken thighs should be skin side up).
Bake 30 minutes. Add broccoli to sheet pan; stir to coat broccoli with pan juices and turn sausage. Bake 30 minutes or until broccoli is beginning to brown and chicken is cooked through (165°F).
