We had this last night which made me think to post it. It’s more method than recipe, and it couldn’t be simpler. I don’t do pork loins any other way now. Just use your fav. spices, I usually switch out between lemon/pepper, Tony Chachere’s Cajun or Webers Steak 'n Chops depending on how I’m feeling, and they’ve all been excellent! 
http://www.finecooking.com/recipe/perfect-grilled-pork-tenderloin