Mix honey mustard, Italian dressing, oil, salt and pepper in small bowl.
Place pork tenderloin in baking dish.
Cover tenderloin with sauce.
Add water to bottom of baking dish. Adding more water may be necessary later if water evaporates during cooking. You don't want extra sauce to burn on the bottom of the baking dish.
Bake for 30-40 minutes or until oven thermometer reads 145°F You may leave in oven until pork reaches 150-155°F if you prefer it well done.