In a large bowl, whisk together the Greek yogurt, 2 tablespoon of the olive oil, lemon juice, garlic, salt, and pepper.
Add the chicken and toss well to combine.
Cover and refrigerate for at least 30 minutes, or up to 6 hours.
When ready to cook, cut the zucchini and red onion into pieces that can be threaded on a skewer and toss in the remaining 1 tablespoon of olive oil. Season with salt and pepper, to taste.
Thread the chicken, zucchini, and onion onto the skewers.*
Preheat the grill to medium-high heat.
Place the kabobs onto the grill and cook for 13-15 minutes, turning once, until the chicken is cooked through.
Serve and enjoy!
Notes
If you are using wooden skewers, be sure to soak them in water for 15 minutes prior to using/threading the chicken and vegetables so they don't burn.