The Post's Jane Black visited various government cafeterias and rated them. She rated the USDA cafeteria a "D". I'm not sure how much it's changed in the last 10-15 years, since I last got the salad bar (with blue cheese dressing) every day.
When I started work at USDA I was in the Auditor's building, a red brick building from 1867 or so across 14th street from the South building and Administration buildings. Back then there was a small cafeteria on the first floor of the Auditor's building, and the South building had at least 2, maybe 4, cafeterias. In the middle 70's they built a new cafeteria by taking over one of the courtyards between wings 2 and 3, big enough to serve the complex. Once it was complete, they closed the old cafeterias, redid the space and moved my Administrative Services Division to the former site of the 6th floor cafeteria.
The old cafeterias were old-style: one line with limited choices for appetizer/salad, entrees, which were served by attendants, desserts, beverages, and payment at the end. The new cafeteria had more choices and was set up on the scramble system, with different stations for different things. Took a little getting used to.
[Added] I think this is just a small example of the expansion of choice, particularly choice in food, over the last 50 years. We expect lots of choices everywhere, we let and want our children to choose. That's fine, but it also is a factor in obesity.