Food plays a significant role in delineating boundaries between ethnic groups, facilitating the exchange of culinary traditions. The article presents the first analysis of starch granule residues found in the Guanzhong basin dating back to the Spring-and-Autumn period. By examining starch granule discovered on the inner surface of pottery excavated at the Liujiawa site, the capital of the Rui State, this study addresses gaps in the understanding of culinary practices during the Eastern Zhou period in the Guanzhong region. Moreover, it provides new insights into potential cultural interactions during this dynamic period. The identification results suggest a significant utilization of Panicoideae, potentially encompassing foxtail millet, broomcorn millet, and Job's tears, alongside oats. Additionally, Triticeae, which includes wheat, barley, and related crops, emerges as a relatively prominent food resource in the region. The presence of oats at the Liujiawa site is suggestive of interactions and cultural exchanges with northern populations, corroborating with other lines of archaeological evidence related to the same vassal state. This research sheds light on the multifaceted interplay of food, culture, and migration during the Spring-and-Autumn period, revealing the complexities of culinary traditions in the region.