Heat up a gas or charcoal grill. Brush the chicken with olive oil and sprinkle both sides with salt and pepper. Place the chicken on the grill over medium heat. Cover the grill; cook 12 to 15 minutes, turning once, until the juice of the chicken is clear when center of thickest part is cut.
Meanwhile, in a medium bowl, stir together the chimichurri ingredients. Serve the chicken topped with chimichurri sauce.