In northeastern Mexico, near Ocampo, Romero’s and Valenzuela’s caves have been central to explanations of agricultural origins in Mesoamerica for more than four decades. Along with caves in Tehuacán and Oaxaca, these "Ocampo caves" have provided almost all of the available evidence for the initial appearance of a number of key Mesoamerican crop plants, including maize, beans, and squash. This article reanalyzes the cultural and temporal context of five crop plant assemblages in the Ocampo caves: maize (Zea mays), bottle gourd (Lagenaria siceraria), and three species of squash (Cucurbita argyrosperma, C. moschata, C. pepo). Fifteen AMS radiocarbon dates on early domesticates both confirm the stratigraphic integrity of the two caves and substantially revise the temporal framework for initial appearance of core domesticates in northeastern Mexico, showing the transition to food production in Tamaulipas took place more recently than previously thought. A substantially foreshortened chronology for Ocampo crop plants confirms the northern periphery role of Tamaulipas in the origins of agriculture in Mexico, while also underscoring the need for establishing AMS-based archaeobotanical sequences across Mesoamerica to gain an adequate context for understanding the temporal, environmental, and cultural contexts of initial plant domestication in the region.