Was really excited yesterday as I picked up a prime brisket from Costco. The results were very disappointing. The point was very good but the flat was dry. I believe I over cooked it. Was a 13 lb packer. I had the probe in the thickest part of the flat. Cooked at a grate temp of 235. Started checking at 185 and ended up pulling it when the flat was reading 201. It was tough from the moment I started probing the flat at 185 and never got any better. In fact, it probably got tougher the longer I cooked it. Any chance this was actually done earlier? Never cooked a prime before so I am just guessing. I simply can't make a good brisket!! Ended up chopping the flat and added a little beef broth and sauce mix to hydrate it some. Edible but far from good.