Lopez-Alt found that a simmer at around 190 degrees Fahrenheit took about six hours to cook (the high end of a simmer only took three), and the corned beef came out drier at 205 degrees Fahrenheit. It can also simmer in a Dutch oven, covered in a few inches of water at 200 degrees, with the lid cracked, which will keep the water at approximately 180 degrees, yielding nicely-textured corned beef in around 10 hours.