This dissertation explores the structure, origins, and theological meaning of the rites of preparing the Eucharistic gifts of bread and wine in the East Syriac tradition. The East Syriac tradition is unique in that these rites are specified in great detail, down to the ingredients in the bread and instructions for how the loaves should be baked; these are not mere prescriptions found in canonical legislation, but actual rubrics in a liturgical service. While scholars have focused on one of the ingredients in the Eucharistic bread – the Malkā or Holy Leaven – and have only tangentially touched on the Preparatory Services, this dissertation provides an original scholarly contribution to the fields of liturgical studies, Syriac studies, and theology by examining the manuscript sources of these Preparatory Rites, in order to shed light on the questions of when and where the services first emerged, how they evolved, and how they have been interpreted theologically. The dissertation includes a critical edition of the rites and an English translation, as well as of the rite of the Renewal of the Holy Leaven, which shares numerous structural similarities with the Preparatory Rites. The dissertation goes on to present a structural analysis of several liturgical units within the Services of Preparation. Next, the dissertation examines evidence from several genres, including canonical collections, casuistic literature, theological commentaries, and archaeology, in addition to liturgical texts, to shed as much light as possible on how the rites evolved. Lastly, the dissertation explores how liturgical commentators in the East Syriac tradition (ancient and modern) have interpreted the Rites of Preparation, as well as making a few points of mystagogical interpretation. Throughout, the dissertation includes comparisons between the Preparatory Services in the East Syriac tradition and those in other Christian ritual traditions (Armenian, Byzantine, Coptic, Ethiopian, Maronite Syriac, West Syriac, and Latin). All in all, this dissertation aims to be useful, not only to scholars of liturgical studies or of the Eastern Churches, but also to the living tradition of the Church of the East, which continues to use the very rites under discussion before every celebration of the Eucharist.