It is a good idea to put about 1/2 inch between chunks of food on your kebab. It can help everything cook through more quickly.
But the very best way would be to cook meat and vegetables on different skewers. That’s because veggies and meats can need different cooking times to be done, says chef and food science whiz Alton Brown. Plus, it cuts back on the chance of germs moving between the meat and veggies.
Try putting slow-cooking veggies like sweet potatoes on one kebab, fast-cookers like zucchini and mushrooms on another, and meat on another.
However, most people cook them all together. That's OK. The risk of germ mixing is small when you make sure everything is well-cooked. Keep cooking and turning your kebabs until the meat is firm, but yielding.