The cooking time for corned beef depends on the method used, states the United States Department of Agriculture. For example, corned beef that is made using an oven or a stovetop is typically cooked for approximately 1 hour per pound.
If using an oven cooking bag to cook corned beef, the USDA recommends cooking for 2 1/2 to 3 hours for a 2- to 3-pound beef brisket and 3 to 3 1/2 hours for a brisket that is 3 to 5 pounds. Corned beef in a slow cooker can be cooked for 5 to 6 hours on high and 10 to 12 hours on low. If using a microwave, corned beef should be cooked for 20 to 30 minutes per pound of meat.