McNellis has been the Senior Advisor for Primary Care at the Agency for Healthcare Research and Quality (AHRQ) since November 2012. He was a Visiting Senior Scholar at AHRQ from 2011 to 2012 serving as a medical officer supporting the U.S. Preventive Services Task Force.

Previously McNellis spent 12 years at the American Academy of Physician Assistants, most recently as Vice President for Science and Public Health. He completed a fellowship in primary health care policy in 2003.

From 1992-2000 McNellis was on faculty at the George Washington University (GW) Physician Assistant Program. While at GW he served as director of research, academic coordinator and acting director. In 1999 he received the Master Teacher Award from the Association of PA Programs.

McNellis graduated from GW’s PA program in 1990 and worked as a PA in a variety of clinical and research settings.