What is a good substitute for ground veal?

The original recipe calls for a total of 2 lbs of ground meat, 1/2 beef and 1/2 veal.

I would suggest a close approximation to the effect can be had by using either (in decreasing order of preference):

• 50% ground pork, 50% ground beef -- Some of the mild flavor of veal, with tenderness and flavor from the pork
• 100% ground beef -- It won't be as tender or as subtle, but still will be good

I would avoid trying to use as part of your substitution mixture:

• Ground lamb, goat, ox, and so on -- flavor is too strong
• Ground chicken or turkey -- these are extremely low in fat, likely to toughen your overall mixture, and likely to make it taste more poultryesque

Personally, I would also switch from whole eggs to just the yolks, which will bring the binding and tenderizing qualities of the yolk, without the slightly rubber-like texture of albumin based white, to more closely approximate the qualities the veal would have brought to the dish.

I have used ground turkey as a substitute in several receipes with ground beef . I have never had a poultryesque (did I spell that right) taste, especially when you are using quite a bit of seasoning (and stout in this receipe.) Ground turkey is low fat, readily available and tasty. I recommend it heartily!