In a blender or food processor, combine the orange juice, lime juice, olive oil, cilantro, mint, oregano, cumin, and garlic.
Blend until smooth and well combined.
Place the pork loin in a large resealable bag or bowl and pour the marinade over the top, making sure the loin is well coated.
Cover and refrigerate overnight.
Before cooking, remove the pork loin from the marinade and place it on a wire rack to allow any excess marinade to drip off.
Preheat the pellet grill or oven to 425°F.
Season the outside of the pork loin generously with the salt and pepper blend, coating all sides.
Place the loin on the pellet grill or in the oven and cook at 425°F for 30 minutes.
Reduce the temperature to 375°F and continue cooking for approximately 45 minutes, or until the internal temperature reaches 145°F.
Remove the pork loin from the grill or oven and allow it to rest for 5 minutes before slicing and serving.