For chimichurri, place 1 cup parsley, the garlic, 3/4 teaspoon salt and 1/2 teaspoon pepper in food processor container. Cover and process with on/off turns just until finely chopped. Add the vinegar and process to combine. Slowly add oil and water in a thin stream with the machine running. If necessary, adjust flavor by adding more salt and/or pepper (chimichurri should be a highly seasoned mixture).
Place pork tenderloins in large, resealable plastic bag. Pour half (about 1/2 cup) chimichurri over pork; close bag to seal. Turn bag to evenly coat pork with marinade. Refrigerate for 30-60 minutes, turning bag occasionally. Transfer remaining chimichurri to a serving bowl.
Prepare a medium-hot fire in grill. Brush grill rack with oil. Remove pork from marinade; discarding marinade in bag. Place tenderloins diagonally on bars of the hot grill rack. Grill tenderloins, uncovered, over direct heat for 20 minutes or until internal temperature reaches 145°F, turning every 3-4 minutes with tongs.
Transfer pork tenderloins to cutting board. Loosely cover with foil; let rest for 5 minutes.
To serve, cut pork tenderloins into thin slices; arrange on dinner plates. Stir “remaining” or “set aside” chimichurri; spoon over pork. If desired, garnish with parsley sprigs.