This article is an anthropological history of the bar/bat mitzvah ceremony in the Yishuv and Israel of the 1940s and the 1950s, when this ceremony radically grew in terms of the space, time, and economic resources devoted to it, as well as expanded to include girls. To explain that shift, I suggest distinguishing classic rites of initiation from the system of life-cycle ceremonies typical of modern consumer culture, which emphasizes the transition between temporal markers rather than social statuses and imposes no task on the birthday celebrant. The article reconstructs the process by which, during the 1940s and the 1950s, the bar/bat mitzvah ceremony came to function more as an elaborate birthday party than as a rite of initiation. The historical reconstruction demonstrates how, during the late Mandate period and early years of statehood, a new grassroots Israeli culture emerged, shaped by the accommodation of Western consumer culture to Jewish traditions rather than by Zionist ideology or established religion.