A 4-pound chicken takes between 90 minutes and two hours to cook fully. This cooking time varies depending on oven temperature and whether the chicken is stuffed.
When roasting a whole chicken in the oven, preheat the oven temperature to 375 degrees Fahrenheit. At this temperature, a 4-pound chicken takes about an hour to cook fully. In order to verify that the chicken is cooked all the way through, use a thermometer with a probe to check the internal temperature. Insert the thermometer near the breast without touching the bone. It should measure at least 180 degrees Fahrenheit. Any juices that run from the pierced meat are clear when the chicken is cooked.