Vegetarian and Vegan are on the menu, but the same kitchen also prepares what you avoid, so cross-contamination is possible. Tell staff what you react to, and ask how your dish is prepared before you order.
A burger restaurant on the Burggasse in Vienna's Neubau that says it cooks with organic ingredients, buns from an organic bakery and meat from small family farms. Vegetarian and vegan burgers rotate monthly, built on chickpeas, quinoa, tofu or lentils. One kitchen for everything, so ask before ordering.