Corned Beef Brisket Prepare from THAWED state for best results. Product may be refrigerated up to 3 days prior to use. Individual appliance cooking time will vary. Adjust cooking time accordingly. Microwave: Do not remove or pierce plastic film. Place tray in microwave. Heat on high for 2½ to 3½ minutes. Film will expand and form a bubble during heating, then self vent and slowly relax over brisket. Remove from microwave and let rest for 2 minutes. Caution, contents are very hot!