烤肉 is both a noun for 'barbecued/roasted meat' and a verb-object compound (离合词) meaning 'to barbecue/roast meat'. As a separable verb, you can insert measure words or modifiers between 烤 and 肉, such as 烤一次肉 ('barbecue once') or 烤了很多肉 ('barbecued a lot of meat').