In a large bowl, mix Greek yogurt, olive oil, garlic, lemon juice, oregano, salt, and pepper until well combined.
Add the chicken breasts to the bowl and ensure they are fully coated with the yogurt mixture.
Cover the bowl and let the chicken marinate in the fridge for at least 30 minutes, or up to overnight for best results.
Preheat your oven to 375°F (190°C).
Place marinated chicken breasts on a baking sheet lined with parchment paper.
Bake in the preheated oven for 25 minutes or until the chicken is fully cooked and no longer pink in the center.
Remove from the oven and let rest for 5 minutes before serving.