In a bowl, combine parsley, cilantro, garlic, red wine vinegar, olive oil, red pepper flakes, oregano, salt, and black pepper. Set aside half of the chimichurri in a jar, cover, and refrigerate for serving later.
1 cup fresh parsley, 1 cup fresh cilantro, 3 cloves garlic, 3 tablespoons red wine vinegar, ½ cup olive oil, ½ teaspoon red pepper flakes, 1 ½ teaspoons dried oregano, 1 ½ teaspoons salt, ¾ teaspoon black pepper