Robert W. Quesal, Ph.D., professor in the Department of Communication Sciences and Disorders, is coauthor of OASES – the Overall Assessment of the Speaker's Experience of Stuttering published by NCS Pearson, Inc. in January, 2008. The OASES, an assessment tool designed for individuals age 18 and older, is a collaborative effort between Dr. Quesal and J. Scott Yaruss, Ph.D., an Associate Professor the Department of Communication Science and Disorders at the University of Pittsburgh.

OASES has been in development for over ten years. Its creation was spurred by the American Speech-Language-Hearing Association's focus on treatment outcomes and evidence-based practice in the mid-1990s. There has been a need to develop good tools to assess the more difficult to measure aspects of the stuttering disorder, commonly referred to as cognitive (the thoughts and self-evaluations of the person who stutters) and affective (the feelings of the person who stutters) features of stuttering. Most assessment tools focus on surface disfluency, which, while being the most noticeable past of stuttering, is often not the most important to the person who stutters, and is often not the most debilitating part of the disorder. The OASES is based on the World Health Organization's International Classification of Functioning, Disability, and Health (ICF) and its precursor, the International Classification of Impairment, Disability, and Handicap (ICIDH). The ICF provides an internationally recognized theoretical framework for understanding health conditions, like stuttering, and was used to guide the development of the instrument.

Yaruss and Quesal collaborated on a number of different versions of the assessment tool, beginning with three separate instruments, Functional Communication and Stuttering (FCS), Speaker's Reactions to Stuttering (SRS) and Quality of Life and Stuttering (QOL-S). After gathering data on the separate scales, the authors determined that the three scales could be combined into a single instrument, originally called the Comprehensive Assessment of the Speaker's Experience of Stuttering (CASES), which was further refined into the 100-item OASES. The final scale has four sections: General Information, Your Reactions to Stuttering, Communication in Daily Situations, and Quality of Life. In total, over 300 people who stutter comprised the sample population for the scales, with nearly 200 in the normative sample for OASES. The validity of the OASES was established over the course of its development, and the final scale has strong internal consistency, test-retest reliability, and construct validity. Importantly, the test can be administered in approximately 15 minutes, yet still provides a wealth of information relating to the totality of the stuttering disorder. Results are summarized as “impact scores” which describe stuttering's impact on a range from mild to severe. Test information can help speech-language pathologists to design treatment and write appropriate treatment goals for their adult clients who stutter. Yaruss, Quesal, and a third colleague, Craig Coleman from the Children's Hospital of Pittsburgh, are currently working on teen and school-age versions of the OASES.

Quesal's interest in under-the-surface features of stuttering goes back over 30 years. As a person who stutters himself, he did not receive good speech therapy until he was an undergraduate student at Indiana University. The treatment he received at IU addressed more than surface fluency. Quesal realized, however, that many of the changes that took place as a result of the treatment he received were not easily observed by others. His Master's thesis topic was attitudes in stuttering, and the topic has been his primary interest throughout his career. In many ways, the publication of the OASES is the culmination of his life's work.