How to Make It
Preheat grill to high (450°F to 500°F). Drizzle pork with 1½ tablespoon oil and season all over with 1 teaspoons salt and 1 teaspoon pepper. Grill pork, covered, turning every 5 minutes, until a meat thermometer inserted in thickest portion registers 140°F, 16 to 18 minutes. Remove from grill and let rest 5 minutes.
Meanwhile, toss mini peppers with 1 tablespoon oil. Grill, turning once, until charred on both sides, 2 to 3 minutes per side. Transfer to a medium bowl and add basil, vinegar, oregano, garlic, and remaining 3 tablespoons oil, ½ teaspoon salt, and ¼ teaspoon pepper. Let marinate 10 minutes.
Slice pork and serve with marinated peppers.