I've not seen it any DC Metro restaurant but it's easy enough to make yourself. It's got rye, whole wheat flour, molasses, and cornmeal in it. Some people add raisins, but to me that makes it a baked version of Boston Brown Bread.
Maybe you'd like the brown bread at Cheesecake Factory?
re: Transplanted Texan
It's one of those places where you have to go at off times to avoid the lines. One of my relatives absolutely loves it and we go there to celebrate her birthday. I do like some of the items on their small plates menu and their bread. In winter they offer a pumpkin cheesecake, which is less sweet and better than their other cheesecakes (IMO). CF is certainly a higher quality chain than TGIF, Bennigans, etc. I've always thought they should call it "Garlic Factory" since there seems to be garlic in everything but the cheesecake!
6975 Security Blvd, Windsor Mill, MD 21244