In a mixing bowl, combine olive oil, minced garlic, dried oregano, ground cumin, salt, and pepper. Add the boneless, skinless chicken breasts to the mixture, ensuring they are well coated. Cover the bowl and let the chicken marinate in the refrigerator for at least 30 minutes.

Preheat your grill or skillet to medium-high heat, around 375°F. Once hot, place the marinated chicken on the grill or skillet and cook for 6–7 minutes per side until it reaches an internal temperature of 165°F. Let the chicken rest for 5 minutes before slicing it thinly.

In a small bowl, whisk together plain Greek yogurt and fresh lemon juice until smooth and creamy. Set it aside to allow the flavors to meld together.

In a mixing bowl, combine diced tomatoes, cucumber, finely chopped red onion, sliced kalamata olives, and crumbled feta cheese. Toss gently until everything is well mixed.

Heat corn tortillas or soft taco shells on a dry skillet over medium heat for a few seconds on each side. You want them warm and pliable.

Take a warm tortilla and layer it with sliced, grilled chicken. Top with the vibrant vegetable mixture and drizzle the tangy yogurt sauce over everything.

Sprinkle chopped fresh parsley over the assembled tacos for a pop of color and fresh flavor. Serve immediately.