When cooking Cornish hens, it is important to ensure that the internal temperature reaches at least 165°F (74°C). This can take anywhere from 40-60 minutes, depending on the size and weight of your hen.   To confirm that the internal temperature has reached the desired level, you can use a meat thermometer inserted into the thigh. Once the temperature has been reached, the hen is ready to be served and enjoyed. Be sure not to overcook your hen, as it can become dry and unappetizing.