Until it's done. ;-)
Don't you just HATE it when cookbooks say that?
Brisket need looonnnngggg loooowwww slooooow cooking to break down the collegen fibers. So cook it covered, with some sort of liquid on the bottom of the roasting pan. Roast at 200-300F until it is fork tender, anywhere from 3 - 10+ hours, depending on the heat you pick.
Don't you just HATE it when cookbooks say that?
Brisket need looonnnngggg loooowwww slooooow cooking to break down the collegen fibers. So cook it covered, with some sort of liquid on the bottom of the roasting pan. Roast at 200-300F until it is fork tender, anywhere from 3 - 10+ hours, depending on the heat you pick.