Set your Z Grills Pellet Grill to 275°F.
Cut open packaging of corned beef and drain off liquid. Be sure to grab the spice packet included with the brisket. Gently rinse off corned beef and then pat dry with a paper towel.
Open the spice packet with your corned beef, sprinkle contents over the brisket, and then sprinkle a light dusting of black pepper according to your preference.
Once the pellet grill has reached temperature, insert probes into corned beef brisket pieces. If you only have a single probe, insert that probe in the center of the smallest piece because it will cook the fastest.
Smoke for 3 to 4 hours until corned beef reaches an internal temperature of 175°F. Next, transfer briskets to an aluminum pan and pour just enough beer in to cover the bottom of the pan. Cover with foil leaving one corner open to let out steam.
Continue cooking for another 2-3 hours until internal temperature reaches about 205°F. Use an instant-read thermometer and poke different parts of the brisket, checking for tenderness. If the probe goes into the meat with very little tension, it is done. If not, continue cooking until it becomes tender.
Once the meat is tender and fully cooked, remove the pan from the pellet grill and let the corned beef rest for about 30 minutes, still covered with one corner open to prevent overcooking.
Slice corned beef into 1/8-inch slices cutting against the grains of the brisket. If brisket crumbles, make slices a little thicker.