Cooked foods including chicken should not sit out for longer than two hours, according to the USDA, and if the temperature is more than 90 degrees Fahrenheit, then one hour is the limit. Chicken or other foods left out longer than that should be discarded.
Food safety experts advise that hot foods should be kept hot and cold foods kept cold until it is time to serve them. Hot items should be placed into the refrigerator cool, not hot, to inhibit bacteria growth, and foods should be covered after they are cooled, not before. Leftovers should always be properly reheated all the way through to kill off any bacteria that might be present.