[4] In 2005, she moved to the Environmental Protection Agency (EPA), where she was the principal deputy assistant administrator of the Office of Enforcement and Compliance Assurance.

Nevertheless, McCabe stated that agency staff would "continue to do our best to ensure that this agency’s decisions and actions are based on our two bedrock principles: carrying out the law and ensuring that the best science informs all that we do.”[10] In December 2017, New Jersey governor-elect Phil Murphy announced he would nominate McCabe to serve as commissioner of the New Jersey Department of Environmental Protection (NJDEP).

[7] Environmental groups New Jersey Sierra Club and Clean Water Action supported McCabe's nomination, which was approved on June 7, 2018.

[11] During her time in office, NJDEP filed 13 major natural resource damages lawsuits against polluters, became a national leader in addressing contamination from per- and poly-fluoroalkyl substances (PFAS), helped to address the Newark lead water crisis, coordinated passage of a landmark environmental justice law, spearheaded New Jersey's return to the Regional Greenhouse Gas Initiative (RGGI), released the state's first comprehensive scientific report on expected local impacts of climate change, and put forward a roadmap of recommendations for cutting greenhouse gas emissions.

[13] On August 30, 2018, McCabe signed an administrative order that closed "all lands owned, managed or otherwise controlled" by the New Jersey Department of Environmental Protection to black bear hunting.