Exclusionary discipline practices differentially harm young children of color. As early childhood education systems seek to close these gaps to ensure all young children have access to high quality early learning experiences, the field requires more evidence-based approaches that can be scaled and replicated. Infant and early childhood mental health consultation (IECMHC) has been associated with lower rates of preschool expulsion; but the field lacks clear guidance on the essential elements of high quality IECMHC. Without such guidance, researchers cannot build a credible evidence base for the causal link between IECMHC and exclusionary discipline. An interdisciplinary research team, with support from the national Center for Excellence in IECMHC, led a consensus-building process to identify the essential activities of IECMHC as implemented across settings. The three-stage Delphi Process resulted in a list of five essential elements and 26 activities that define IECMHC and make concrete its emphasis on relationships and equity. This greater clarity around the activities of IECMHC can help inform future research and evaluation, as well as workforce and professional development. [This paper was published in "Early Childhood Research Quarterly" v66 p24-33 2024.]