Quorn contains eggs, milk and what the manufacturer coyly describes as "a tiny relative of the mushroom" so verify that your baby can tolerate eggs, cows milk and mushrooms first.
My vegetarian baby (a while ago now) had mainly just individual vegetables and fruit for the first few months of weaning, then various kinds of carbs, and then more complex combinations which eventually included Quorn.
I know being sensitive to Quorn is a thing but I think it's a lot rarer than people on mumsnet make out. That's probably to be expected if people who are sensitive to it are very vocal about it but it doesn't really register a an issue for everyone else.