Preheat oven to 400 degrees
Add 1 tsp salt to 1.5 cups boiling water, add potato, celery, carrot, onion and green pepper
Simmer for about 10 minutes until tender crisp
Drain and reserve broth – if needed add water to make 1 ½ cups.
Mix drained vegetables, tomato, mushrooms and fish and place in a lightly greased 2 qt casseroles dish.
Melt butter in sauce pan and blend in flour and oregano.
Gradually add reserved broth stirring over medium heat until thickened.
Add salt and pepper.
Pour sauce over casserole.
Arrange pie crust or biscuits or mashed potatoes over top.
Bake 20-25 minutes or until crust is brown.
