In or before August 1945 Tilly Spiegel returned to Vienna where the Communist Party was no longer banned. Indeed, the Soviets had used their influence with the other occupying powers to ensure that there were seven communists in the new government. She rejoined the party's city leadership team ("Bezirksleitung"), remaining a member of it between 1945 and 1968. In addition, she quickly engaged in the work of building up what subsequently became the &lt;a href="Documentation%20Centre%20of%20Austrian%20Resistance"&gt;Documents Archive of the Austrian Resistance ("Dokumentationsarchiv des österreichischen Widerstandes" / DÖW)&lt;/a&gt;. She worked closely with the DÖW's head of research, . Others involved included her former resistance comrade, Selma Steinmetz, along with Jonny Moser and Herbert Rosenkranz. During the 1960s these, Spiegel and the others were among the first researchers into Austria's National Socialist period to focus on the regime's victims. Moser investigated the persecution of Jews while Steinmetz concentrated on government treatment of the Sinti and Romani people. Spiegel worked on what had happened to women and girls engaged in antifascist resistance and Rosenkranz studied Austria's experience of the November 1938 pogrom ("Kristallnacht"). During the later 1960s, even before the crushing of the Prague Spring, Spiegel seems to have engaged in major "inner-party criticism" over the path taken by postwar communism. Little is known of her final years.