In a mixing bowl, combine yogurt, olive oil, lemon juice, garlic, paprika, cumin, salt, and black pepper. Whisk until smooth.

Add the chicken cubes to the marinade, ensuring they are well coated. Cover and refrigerate for at least 30 minutes, or up to 2 hours for more flavor.

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

Thread the marinated chicken and optional vegetables onto the skewers, alternating between chicken and vegetables.

Preheat the grill to medium-high heat. Place the skewers on the grill and cook for about 10-15 minutes, turning occasionally, until the chicken is cooked through and has nice grill marks.

Remove from the grill and let rest for a few minutes before serving.