Heat 1 tablespoon oil in a large skillet over high heat. Add 1 tenderloin; cook, turning occasionally, until browned on all sides, about 3 to 5 minutes. Transfer tenderloin to a roasting pan. Repeat with remaining oil and tenderloin.
Insert meat thermometer into thickest part of 1 tenderloin. Roast until temperature registers 145°, 35 to 40 minutes for medium rare. Transfer beef to cutting board; let stand 10 minutes. Carve into 1-inch-thick slices. Sprinkle with parsley and serve with mustard.