
Make the chimichurri sauce. Add the parsley, oregano, chili pepper, garlic, olive oil, vinegar, salt, and pepper to a small bowl. Stir together. Note: You can also prepare the chimichurri sauce a day in advance and store in the fridge.
Marinate the chicken. Place the chicken in a bowl and pour about ⅓ of the chimichurri sauce on top. Make sure the chicken pieces are well coated, then cover and marinate in the fridge for 20 to 30 minutes.
Cook the chicken. Heat an outdoor grill or indoor grill pan over medium-high heat. Oil the grates, then grill the chicken for about 4 to 6 minutes per side, until the internal temperature reaches 165°F (75°C). Alternatively, you can cook the chicken in a skillet.
Top with sauce and serve. Transfer the chicken to a serving plate and spoon the remaining chimichurri sauce on top.