O’Neill’s interdisciplinary research and teaching focuses on land use, climate and resilience. She examines state and local government efforts to mitigate the impacts of climate change while also addressing inequality. O’Neill is the principal investigator on a study of land use regulation in cities and exurban areas, the Comprehensive Assessment of Land Use Entitlements Study (CALES). The CALES contributes new data to housing policy debates about which regulations promote housing affordability, integration and reducing greenhouse gas emissions. The Silicon Valley Community Foundation, Chan Zuckerberg Initiative, California Community Foundation and California’s Air Resources Board have provided support for the CALES. Most recently, with support from the Robert Wood Johnson Foundation, she is collaborating with UCLA scholars to explore how CALES data, in conjunction with other research methods, can inform fair housing questions.
O'Neill’s research on sustainable public school meal reform initiatives has supported district-level and state policy implementation of sustainable school meal improvements to promote healthy eating and a circular food system. California’s Department of Food and Agriculture, the Stupski Foundation, the Berkeley Food Institute and Columbia University’s Population Research Center supported this work. Relatedly, O’Neill serves on the steering committee of Virginia Food for Virginia Kids, a collaboration between the Department of Education, other state departments and nonprofits to increase K-12 student access to healthy, Virginia-sourced food.