Costco's American Wagyu Reserve Beef Loin Tenderloin Steak is a premium cut sold by the pound at the warehouse meat counter. American Wagyu beef is produced by crossbreeding Japanese Wagyu cattle with American breeds, combining the extraordinary marbling and rich intramuscular fat of Japanese genetics with the robust flavor profile of American beef. The result is a step above USDA Prime in tenderness and marbling without the extreme fat content of full A5 Wagyu.

The beef loin tenderloin is widely regarded as the most tender cut on the animal, running along the underside of the spine in the short loin primal. Because this muscle does almost no work, it develops virtually no connective tissue, yielding a buttery, fine-grained texture that is unrivaled among beef cuts. The American Wagyu Reserve designation indicates a premium selection tier within Costco's Wagyu program, chosen for superior marbling and quality standards.

This cut is exceptionally versatile: it can be sliced into filet mignon steaks 1 to 2 inches thick for pan-searing or grilling, prepared as a whole roast (chateaubriand style) for special occasions, or cut into tenderloin medallions. For best results, cook to medium-rare (125–130°F internal temperature) and allow to rest before slicing. The mild, delicate beef flavor pairs well with simple seasonings, compound butters, red wine reductions, or classic Béarnaise sauce.