Executive Officers

Ravi Hundal, MD
President & Chief Executive Officer

We are excited to share that Ravi Hundal, MD has been appointed by the John Muir Medical Group Board of Directors to lead JMMG as the next President-CEO effective September 6, 2026.

Dr. Hundal is an accomplished family physician with over 35 years of clinical and executive experience in health care. He brings seasoned judgement, local network/systems experience, and the leadership required to lead JMMG in its next phase of growth continuing the group’s mission to provide high quality, compassionate care to our community.

With more than 18 years of C-Suite executive leadership, his previous JMMG executive positions include Chief Financial Officer and Executive Vice President of Clinical Integration and Population Health since 2008, where his primary responsibilities included managing the company’s finances, financial planning, management of financial risks, and strategic growth. Dr. Hundal served as a JMMG voting board member from 1999-2010.

Dr. Hundal is a long-term Board member of America’s Physicians Group, a national medical group organization. He also currently chairs the Blue Cross California Physician Relations Committee.

Dr. Hundal also has extensive prior board experience including serving on the John Muir Health board from 2013 to 2023, as well as the John Muir Physicians Network board from 2008 to 2013. He has been on and chaired several JMH Boards/committees including the Medicare MSSP, Medicare Advantage/CIN ACO and the VBC Council. From 1999 to 2005 he served as a board member of The Seven Hills School in Walnut Creek.

Dr. Hundal received his medical degree from The Universidad Autonoma de Guadalajara and completed his family medicine residency at Contra Costa Regional Medical Center in Martinez, CA.  He received his bachelor’s degree in biology from the University of California Davis.

Please join us in congratulating him on his new position.

Theresa Harrington
Chief Financial Officer

With more than thirty-five years of progressively responsible experience in accounting, finance and auditing, Theresa brings a wealth of experience and knowledge to the role of Chief Financial Officer for John Muir Medical Group.

Theresa Harrington joined John Muir Medical Group in 2018 as Controller and Executive Director of Administrative Services reporting directly to the Chief Financial Officer.  In this role Theresa established the organization’s first internal Accounting and Finance Department, transitioned accounting and financial reporting to Workday, and automated key compensation and benefit processes.  Her responsibilities have included directing all activities related to accounting, financial reporting, annual operating budget, external financial statement audits and the administration of the Group’s Compensation Program.

Prior to joining John Muir Medical Group, Theresa spent nearly two decades with John Muir Health serving as a Director of Finance, Director of Internal Audit and Director of General Accounting.  Before that she worked in the banking industry and public accounting.

Theresa earned a Bachelor of Arts degree in Business Economics with a concentration in Accounting from the University of California, Santa Barbara and holds a CPA designation (currently inactive status) with the California Board of Accountancy.

Tanya Threewitt, MD
Chief Operating Officer and Senior Vice President

Tanya Threewitt, M.D. joined John Muir Medical Group in 2002 and has dedicated 23 years of progressive experience to the Group. She became Chief Operating Officer and Senior Vice President in May 2026. Her primary role is to lead operational strategy and execution, overseeing all aspects of ambulatory and hospitalist operations, ensuring clinical excellence, financial sustainability, and alignment with the group’s mission to improve community health.

In January of 2023, Dr. Threewitt began serving as Vice President of Ambulatory Health, overseeing operations at 29 primary care practices, managing 175 clinicians and seven direct reports. She was heavily engaged in long-term planning for ambulatory health specialties, ensuring alignment with the health system strategy. She executed initiatives to provide more effective, efficient care that improved patient health while lowering overall healthcare costs. She led organization-wide process improvement initiatives applying Lean Six Sigma methodologies to define problems, streamline workflows, and drive measurable success. She advanced team-based care models by strengthening collaboration between physicians, nurse practitioners, and physician assistants, building trust, addressing liability concerns, and expanding NPs/PAs into primary care clinics.

As Executive Medical Director of Ambulatory Operations from (Apr 2017 – Dec 2022), Dr. Threewitt oversaw 35 primary care and five urgent care practices with 11 direct reports. She developed strategic plans for urgent care, pediatrics, family medicine, and internal medicine. She managed budgets to reduce costs and allocated resources for staffing and clinic needs.

From (Jan 2015 to Mar 2017) as Medical Director of Ambulatory Operations and Family Medicine, Dr. Threewitt oversaw 35 primary care clinics, addressing compliance issues, onboarding new hires, and managing call pools and float coverage. She standardized clinical workflows across all sites and developed strategic initiatives to increase patient volumes and support sustainable business growth.

Dr. Threewitt was Associate Medical Director of Family Medicine from (Jan 2014 – Jan 2015) and served as an SME for all family medicine related matters. From (Jan 2008 to Jan 2014) she served as Associate Medical Director of Information Technology and successfully implemented CernerEHR, followed by a transition to Epic EHR, enhancing health record management and clinical interoperability. She served as a strategic advisor to IT teams, providing physician-level insight to optimize usability and workflow integration.

Dr. Threewitt currently sits on the John Muir Health Value Based Care Council and the John Muir Health Strategic Planning and Marketing Committee.  From 2013 – 2018 she served as co-chair of the Physician Strategic Council. She sat on the Board of Directors for John Muir Medical Group from 2011 – 2021, serving as Board Vice Chair from 2014 – 2021.

Dr. Threewitt holds Lean Six Sigma Certification (Yellow Belt) from Lean Six Sigma Institute. She completed a Fellowship inHealthcare Leadership, from the California Healthcare Foundation

Born and raised in San Jose, California, Dr. Threewitt received an undergraduate degree in psychology from UC Davis. She graduated from Hahnemann Medical School in Philadelphia and completed her Family Medicine residency through UC Davis in Modesto, California at the Stanislaus County Doctor’s Medical Center.

Dr. Threewitt lives in Clayton, CA with her husband and enjoys travel, live theater and all things Science Fiction/Fantasy.