Start by whisking together olive oil, lemon juice, crushed garlic, oregano, salt, and black pepper in a mixing bowl. Make sure everything is well combined to coat the chicken evenly. Slice the chicken into evenly sized 1-inch cubes. Add the chicken to the marinade, stirring or tossing to coat thoroughly. Cover the bowl with plastic wrap or seal it in a freezer bag. Place it in the fridge to marinate for at least 4 hours or overnight for maximum flavor.
If using wooden skewers, soak them in water for at least 30 minutes before use. This prevents them from burning on the grill. Once your skewers are ready, thread the marinated chicken onto them. You can also add onion slices between the chicken pieces for added sweetness and texture.
Preheat your grill or grill pan to medium-high heat. Lightly brush the grates with oil to keep the chicken from sticking. Place the skewers on the grill and cook for about 10-15 minutes, turning frequently to ensure even cooking. The chicken should be golden with slight charring and reach an internal temperature of 165°F.
Carefully remove the skewers from the grill and place them on a platter. Pair your freshly grilled chicken souvlaki with pita, a dollop of tzatziki, and a sprinkle of feta cheese for an irresistible finish!