Preheat oven to 400 degrees F. Coat a shallow roasting pan with cooking spray. Place tenderloins in pan and season all over with salt and black pepper. On 1 of the tenderloins, spread hoisin sauce all over. On the other, drizzle vegetable oil over the top.
Using wooden picks, attach black olives to pearl onions and then the hoisin- coated turkey tenderloin, making a set of eyes in the meat.
Roast 30 minutes, until an instant-read meat thermometer inserted into the tenderloin registers at least 160 degrees F. Reserve plain tenderloin for another meal. Let hoisin-coated turkey stand 10 minutes before slicing crosswise into 1/2-inch thick slices.