Does Taco Bell use grade D meat?
The grade I suspect Taco Bell uses is called “standard-minus.” It’s good meat. It’s “almost devoid” of marbling–flecks of fat through the meat–because the less marbling they have in the meat, the less grease they have to figure out how to get rid of. Besides, almost all Taco Bell meat is ground beef anyway; what would they care about marbling?