We had ours at Maggiano's and it was very reasonable and everyone thought the food was good. We had our own bartender too. Beats a typical hotel dinner by a mile.
Chef Geoff has an area they can close off. Also McCormick & Schmicks and Clyde's in Tysons. There are also places in Old Town that can accommodate a large group - see Opentable for a large party search. 2941 could do it but I doubt its as reasonably priced.
Had a work event for about this number of people at Wildfire in Tyson's Galleria. Really nice space and excellent food. Pricing was similar to Maggiano's but food was much better, IMO.
I have hosted events at Maggiano's before. They do offer a few levels of prix fixe pricing and it's fairly reasonable. The downside is it's pretty standard chain restaurant fare - nothing too gourmet - but the quality and portions are good for what you pay.
A co-worker's son is getting married this May. She and her husband will be paying for the rehearsal dinner and they wanted to get some recommendations for restaurants (either Italian or American fare) in the Fairfax, Fair Oaks, area.
They are looking for venues that would be able to host 30 to 50 people in a private room. If the prices are are are reasonable, that would be great.