Preheat oven to 450°. Pour oil into large roasting pan. Add chicken, onion and mushrooms, turning to coat with oil.
Bake 5 minutes; turn chicken over and stir vegetables. Bake an additional 5 minutes.
Meanwhile, in medium bowl, whisk flour into chicken broth. Add vinegar, lemon juice, salt and pepper, stirring well.
When chicken has cooked for 10 minutes, add broth mixture to roasting pan, cover with foil and bake 10 minutes. Remove foil; stir vegetables and bake, uncovered, until sauce bubbles and is slightly thickened, about 10 minutes.
Heat broiler. Turn chicken over. Place pan 6 inches from heat and broil until chicken just starts to turn golden, about 3 to 5 minutes. Serve immediately.
Please Note: Nutritional values listed may vary from final results depending on actual measurements and brands used to prepare the recipe.