Mix olive oil, lemon juice, lemon zest, black pepper, garlic powder, onion powder, and salt in a bowl.
Place chicken breasts in a resealable bag or shallow dish and pour the marinade over.
Seal the bag or cover the dish, and refrigerate for at least 30 minutes.
Preheat the grill or oven to medium-high heat.
Remove chicken from marinade and discard the leftover marinade.
Place chicken on the grill or in a baking dish.
Cook for 6-7 minutes on each side, until the internal temperature reaches 165°F (75°C).
Remove from heat and let rest for 5 minutes.
Garnish with fresh parsley and serve with lemon slices.