Chiming in a hair late here, but seitan is another good option for vegetarians. There are lots of different brands out there and they all need to be treated differently, though. Some of it comes pre-marinated, too, so check the label.
My favorite brand is probably Gardein. Their homestyle "beef" is quite meaty and neutral enough in flavor that it would soak up a sauce nicely. It isn't designed for marinades, though. (You're supposed to sear it and then simmer it in your sauce or stew. It does take on the flavors, though.)