Rub the chicken breasts with olive oil.
Season with garlic powder, paprika, salt, and black pepper.
Preheat your grill or grill pan to medium-high heat.
Cook the chicken for 6–8 minutes per side, or until the internal temperature reaches 165°F.
In a bowl, mix chopped parsley, cilantro (if using), minced garlic, red wine vinegar, olive oil, red pepper flakes, salt, and pepper.
Alternatively, blend the ingredients in a food processor for a smoother sauce.
Drizzle the chimichurri sauce over the grilled chicken.
Serve with your choice of sides.