In a bowl, combine red wine vinegar, lemon zest and juice, Dijon mustard, minced garlic, dried oregano, salt, and black pepper.

Gradually whisk in the extra virgin olive oil until the mixture is well combined.

Place chicken tenderloins in a zip-top bag or shallow dish and pour the marinade over the chicken.

Seal the bag or cover the dish and marinate in the refrigerator for at least 30 minutes.

Preheat a grill or skillet over medium-high heat.

Remove chicken from the marinade, discarding the marinade.

Cook chicken tenderloins for about 5-7 minutes on each side or until cooked through.

Garnish with fresh oregano, if using, and season with additional salt and black pepper before serving.