Preheat the oven to 325°F
Rinse the corned beef and pat it dry
Place the corned beef fat side up in a roasting pan
Add the spice packet if included
Add 1 to 2 cups of water, broth, or beer to the pan
Cover the pan tightly with foil or a lid
Bake for about 3 to 4 hours, or until tender
Check for doneness with a fork; it should be easy to pierce
If using vegetables, add them during the last 45 to 60 minutes of cooking
Remove the foil for the last 15 to 20 minutes if you want a browned top
Let the corned beef rest for 10 to 15 minutes before slicing
Slice against the grain and serve