In a large bowl, combine Greek yogurt, minced garlic, lemon juice, oregano, olive oil, salt, and pepper to create the marinade. Cut chicken into 1-inch pieces and coat thoroughly. Cover and refrigerate for at least 1 hour, preferably overnight.

If using wooden skewers, soak them in water for about 30 minutes to prevent burning.

Remove chicken from the fridge and thread onto soaked skewers, interspersing with bell pepper and onion chunks for added color.

Preheat grill to medium-high heat (375°F or 190°C) and grill kebabs for 10-12 minutes, turning occasionally until chicken is fully cooked and golden-brown.

Remove kebabs from grill and serve warm, garnished with herbs or lemon wedges.