In his research, Gregg studies the housing outcomes of households with limited financial resources. This research includes projects focused on the effects of the Housing Choice Voucher program, the seasonality of family homelessness, the prevalence of housing cost burden, and the effects of housing stock expansion. He has published housing research in leading journals such as Urban Studies and Housing Policy Debate. Gregg is actively engaged with policymakers, nonprofit organizations, and housing developers on matters related to housing and homelessness in the Puget Sound region.