In a large deep skillet or a Dutch oven, heat 2 tablespoons of the oil over moderate heat. Season the beef with the garlic powder, salt and pepper. Working in batches, sear the beef, turning occasionally, until browned on all sides, 6 to 8 minutes per batch. Transfer to a bowl and repeat with the remaining tenderloin. Return all the meat to the pan, reserving the juices in the bowl.