In a food processor, combine all chimichurri ingredients -pulse for a few seconds to chop ingredients but not fully blend.
Separate chimichurri in half. Brush chicken with half the marinade making sure it’s evenly coated, pour any remaining over the top. Save the other half of the marinade to brush the chicken after grilling it. Do not cross contaminate the marinade with raw chicken.
Marinate chicken in the refrigerator for at least 30 minutes or up to 3 hours.
Preheat and oil your grill or grill pan to medium-high heat.
Remove the chicken breast from the marinade, discard marinade.
Grill the chicken breast for 6-8 minutes per side, or until the internal temperature reaches 165°F (74°C). Time will vary depending on how hot your grill is.
Let the chicken rest for a few minutes before slicing then brush with additional chimichurri.