Despite the expanding use of undergraduate student peer counseling interventions aimed at reducing college student drinking, few programs evaluate peer counselors' competency to conduct these interventions. The present research describes the development and psychometric assessments of the Peer Proficiency Assessment (PEPA), a new tool for examining Motivational Interviewing adherence in undergraduate student peer delivered interventions. Twenty peer delivered sessions were evaluated by master and undergraduate student coders using a cross-validation design to examine peer based alcohol intervention sessions. Assessments revealed high inter-rater reliability between student and master coders and good correlations between previously established fidelity tools. Findings lend support for the use of the PEPA to examine peer counselor competency. The PEPA, training for use, inter-rater reliability information, construct and predictive validity, and tool usefulness are described.