Is this the case even on same cooking surface and therefore the high heat is essentially Kashering the grate? Or are you assuming that one would put the vegetables in a pan or over foil? Is the answer the same if I want to go from Meat to cooking fish? Thank you

Shalom, Thank you for your question. The laws of using the same cooking surface for meat and then dairy is much more strict than using the same coals. The surface itself would need to be koshered – but because the meat sits directly on the metal grill, the grill would need to get so hot it turns white or sparks fly off it. This is very hot indeed – and I doubt that it gets that hot, unless the coals are touching the grill, or very close to it. In any case the grill would need to be totally clean of any remnants of meat residue. This being the case, we do not use the same grill surface for meat and then meat – unless it is totally cleaned, then "blow torched" or the like. As to using the meat grill to cook parve veggie-burgers – this law is more complicated and depends on whether you are Sephardi or Ashkanazi; on whether the grill was used for meat within 24 hours of the veggie burgers; on whether you intend to eat the veggie burgers with milk (cheese-veggie-burgers) or just on meat plates; and on how clean the grill is. Also the law is different (and stricter) in relation to "sharp" spicy foods like onions etc. As you can see with all these variables it would not be practical to write out all the laws here in this short email. Let us just say that it would be easier to cook the parve food in a separate disposable foil pan – even if this is placed on the meat grill, the parve food will remain parve and may be eaten with milk. (Be careful that no meat spills onto or under the foil pan, and that you use parve utensils). As to cooking fish on meat utensils – even though there are people who are strict and do not cook fish on meat pans – the law is that if the meat pans (or in this case the grill) is clean, one may cook fish directly on it. This is normative practice. Blessings.