Place glaze ingredients in a small saucepan. Bring to a simmer over medium low heat. Reduce heat and simmer about 10 minutes until glaze thickens. Season with salt and pepper to taste.
Heat 2 Tablespoons oil in a large oven-proof skillet over medium-high heat.
Add pork tenderloin and sear on all sides until golden brown. Brush entire tenderloin with glaze, place oranges slices over pork.
Place pork in oven and roast for 15-30 minutes until the center of the tenderloin registers 160 degrees F. Brush with additional glaze two more times during the roasting time. Let stand 5 minutes, slice and serve.