In a food processor, pulse the parsley to chop. Add the garlic, 1/2 cup EVOO, 1/2 tsp. dried oregano, the vinegar, red pepper, 1/2 tsp. coarse salt and 1 pinch black pepper; pulse to combine. Transfer to a bowl; let sit for 2 hours.
Preheat a grill to medium-high. Brush the pork with EVOO and rub with 1 tsp. coarse salt, the crumbled oregano and powdered garlic. Grill, turning often, until a meat thermometer inserted into the thickest part registers 145 degrees , about 35 minutes. Let rest for 20 minutes. Thinly slice, then drizzle with the sauce.