No, it is not recommended that you feed casserole to your dog or let them eat it by accident.
The reason being is that casseroles are known to be high in fat and salt content which in turn is really bad for a dogs health.
Also some common ingredients in casseroles include both garlic and onions which are toxic to dogs and could kill them in larger quantities.
Therefore it is best to exercise extreme caution when it comes to casseroles and your dog and avoid them at all costs.
There are much better foods to feed to your dog besides casserole.
So do NOT feed casserole to your dog as per of their diet.