In medium bowl, whisk together apple butter, onion, mustard and wine. Season with salt and pepper to taste.
In small sauce pan, bring apple butter mixture to a boil, stirring constantly. Set aside a few tablespoons of the glaze to drizzle on the cooked meat before serving.
Preheat grill to medium high. Brush pork with oil and season with salt and pepper.
Over direct heat, brown tenderloin on all sides, about 5 minutes total. Brush meat with glaze and, if grill allows, move to indirect heat. Turn every 5 – 6 minutes to prevent glaze from scorching, brushing occasionally with additional glaze. Cook meat to an internal temperature of 160°F (cooking time will vary from 25 – 40 minutes, based on thickness of tenderloins and type of grill).
Remove from grill, brush again with glaze and let rest for 10 minutes. Slice into 1/2-inch thick slices, drizzle with reserved glaze, and serve immediately.