Mix lemon juice, pepper and olive oil for marinade. Pour over chicken in a glass dish with a lid and marinate in the fridge for at least 30 minutes.
Make the Tzatziki sauce by combining yogurt, garlic, lemon juice, cucumber and salt in a bowl and refrigerate until ready to serve.
Preheat grill.
Skewer marinated chicken with the squash, zucchini & red pepper slices.
Grill kebabs over medium heat until chicken is cooked through.
Serve Lemon Pepper Kebabs and veggies with homemade Tzatziki Sauce.