Preheat oven to 350º F. Arrange pork tenderloin slices in a medium skillet.
Prepare the oranges for use by zesting and juicing one orange and slicing the other.
Whisk together orange zest, orange juice, teriyaki sauce, garlic, salt and pepper and pour over pork tenderloin. Roast pork until it reaches 165º F when checked with an internal thermometer, about 20 minutes.
Arrange orange slices on serving platter and place pork tenderloin on top. Spoon pan drippings over pork tenderloin for serving.