Preheat indoor or outdoor grill to medium-high heat. In a small bowl, blend garlic powder, onion powder, salt and pepper until the spices are evenly distributed and then set aside.

Trim pork of excess fat and silver skin and pat dry with paper towels. Season both tenderloins on all sides with spice rub.

Lightly oil grates and prepare outdoor grill for indirect heat. If using a gas grill, turn off burners on one side of grill. If using a charcoal grill, move all of the coals to one side. If using an indoor grill, leave it set to medium heat.

Place pork on the side of grill without direct heat underneath or in center of indoor grill. Cook pork, turning frequently, for about 30 minutes or until it reaches an internal temperature of at least 140 degrees.

Remove pork from grill, cover with foil and allow meat to rest 10 minutes before slicing. During this time, the internal temperature will rise approximately 5 degrees. Uncover, slice and serve.