Costco's Service Deli flap meat is a pre-marinated cut sourced from the bottom sirloin section of the steer, also known as Bavette steak. It arrives at the counter already soaked in a zesty lime and cilantro marinade, ready to cook straight from the package with no additional preparation needed.

Flap meat features long, loosely connected muscle fibers that become exceptionally tender when sliced against the grain. Its open grain structure allows the marinade to penetrate deeply, delivering bold citrus and fresh herb flavor throughout the entire cut. This makes it an outstanding choice for carne asada, fajitas, street tacos, rice bowls, and stir fries.

For best results, grill or sear over medium-high heat and cook to a minimum internal temperature of 145°F, as Costco blade-tenderizes this cut to enhance tenderness. Rest for 5–10 minutes before slicing thinly against the grain to maximize juiciness.