Gather all your ingredients and tools: a large mixing bowl, measuring cups, a whisk, and a baking dish.

In your mixing bowl, combine the olive oil, lemon juice, minced garlic, oregano, salt, black pepper, and red pepper flakes (if using). Whisk together until well blended.

Place the boneless chicken breasts in the baking dish and pour the marinade over them, ensuring each piece is coated evenly.

Cover the dish with plastic wrap and let it marinate in the refrigerator for at least 30 minutes, up to 2 hours for deeper flavor.

Preheat your oven to 400°F (200°C). For a quicker option, you can use an air fryer.

Once preheated, place the marinated chicken in the oven and bake for 25-30 minutes, or until the internal temperature reaches 165°F (75°C) and the chicken is no longer pink.

If using an air fryer, arrange chicken in a single layer and cook at 375°F (190°C) for about 15-20 minutes, flipping halfway through.

Remove the chicken from the oven or air fryer and let it rest for about 5 minutes.

Slice or serve the chicken whole, paired with your favorite veggies or grains like quinoa or brown rice.

Drizzle with additional lemon juice or garnish with fresh herbs for added flavor.