Prepare the Marinade: In a bowl, whisk together the Greek yogurt, olive oil, lemon juice, zest, garlic, and spices until well combined.
Prep the Chicken: Trim excess fat from the chicken thighs and cut them into 1.5-inch cubes.
Assemble the Kabobs: Thread the chicken and red onion chunks onto skewers, leaving space between each piece.
Marinate: Brush the kabobs generously with the marinade, cover, and refrigerate for at least 8 hours or overnight.
Preheat the Grill: Heat your grill to medium-high (375-400°F) and lightly oil the grates to prevent sticking.
Grill the Kabobs: Cook for 10-12 minutes, turning every 3-4 minutes until golden brown and the internal temperature reaches 165°F.
Rest and Serve: Let the kabobs rest for 5 minutes before serving. Enjoy with rice, pita, or a Greek salad.