Remove fat and tough silverskin (fascia) from pork tenderloin.
Coat pork tenderloin in yellow mustard.
Combine salt, pepper, garlic powder, chili powder, oregano, and parsley in a small bowl or shaker. Evenly distribute the dry rub over the tenderloin.
Wrap the tenderloin in plastic wrap and place in refrigerator for 2-24 hours, depending on your timeframe.
Remove tenderloin and allow to reach room temperature by resting on counter for 30 minutes.
Start smoker with wood of your choice and set to a temperature of 200 degrees Fahrenheit.
Heat a large frying pan or skillet over high heat and sear pork tenderloin on all sides.
Place pork tenderloin on smoker. Smoke until internal temperature reaches 145 degrees Fahrenheit for medium rare and 160 degrees Fahrenheit for medium. This will take approximately 2-2.5 hours, but time may vary depending on your smoker set-up. Base cook time off of the internal temperature.
Remove pork tenderloin from heat and let rest 10-15 minutes before slicing.