1.In a medium bowl, whisk together olive oil, lemon juice, garlic, oregano, salt, and black pepper until well combined.
2.Reserve about ¼ cup of the marinade for later use. Place chicken in a resealable bag or shallow dish and pour the remaining marinade over it. Ensure the chicken is well-coated.
3.Seal the bag or cover the dish and refrigerate for at least 1 hour (up to overnight).
4.Preheat grill to medium-high heat (375°F) or oven to 400°F.
5.Remove excess marinade from chicken and cook on the grill for 6-8 minutes per side or roast in the oven for approximately 25-30 minutes until cooked through (internal temperature should reach 165°F).