When I grill these, I do not put them right over direct flames…more like adjacent. I also make sure to spray them with EVOO spray before putting them on the grill due to the low oil content of the marinade-it helps with sticking. I tend to put the tofu and tomatoes furthest from the heat, and the onions, peppers and mushrooms closer, since they are more ‘durable’.
Grill each veggie to the desired level of chary deliciousness, removing each kebab as it is done.