I've posted about The Keg in Waterloo before, but I just visited there this evening and had some additional information to post.
I decided today to have the prime rib, instead of my usual steak option. I always mention to my server that I cannot have gluten, and in this case I specifically questioned the "au jus" that was to accompany the prime rib.
The server didn't know off hand if I could have the au jus, but went to check with the cooking staff. A few minutes later, the host (or manager, I'm not sure which) came to talk to me and mentioned that the au jus contained "corn gluten". He wasn't sure exactly if I could have corn gluten, even though their allergy book indicated that it was fine for Celiacs. (yes, that means they actually have an allergy book. Very cool.)
I did ensure him that "corn gluten" is fine (the word gluten is a little scary, but corn gluten is just corn), and therefore the au jus was fine.
Also, I requested a Caesar salad without croutons, and apparently they made it in a separate bowl so there was no contamination. (The Caesar dressing is safe, I've checked.)
Finally, my meal came with a baked potato and beans and mushrooms. The beans and mushrooms were a little different than the ones my wife (a non-Celiac) got. Hers were cooked in some sort of sauce, and mine were completely plain - probably steamed. I'm not sure exactly why I couldn't have the normal veggies, but they were obviously cautious in preparing my meal.
Overall, it was a great dinner and I really appreciated the staff's knowledge and care about eating gluten-free.