Heat oven to 350 degrees. Place roast in casserole with ... onion soup over meat. Bake covered 2 to 2 1/2 hours, add vegetables. Cover and bake another hour.eat oven to 350 degrees. Place roast in casserole with ... onion soup over meat. Bake covered 2 to 2 1/2 hours, add vegetables. Cover and bake another hour.