Margaret O'Brien holds a bachelor's degree in international relations, which laid the groundwork for her diverse career. Early in her career, she worked as a social worker and real estate agent, gaining valuable experience in community service and client relations. O'Brien served on the City Council of Portage, Michigan, where she honed her leadership and public service skills. Transitioning to the state legislature, she focused on private property rights, education reform, and social issues such as adoption and direct access to physical therapy. O'Brien's legislative efforts extended to public safety, health, and criminal justice, particularly in reforming Michigan's sexual assault laws.

Margaret O'Brien's political identity is marked by a strategic blend of localized policy advocacy with a surprising willingness to collaborate across party lines. Her legislative focus on private property rights and education reform juxtaposes with her progressive stance on issues like female genital mutilation and caregiver training. O'Brien's approach to criminal justice reform, particularly in reshaping Michigan's sexual assault laws post-Larry Nassar, showcases a calculated effort to balance regional industrial interests with broader social justice imperatives.