Empirically supported behavioral treatments cannot be effectively disseminated without understanding key quality components. Mechanism-informed quality measures have extraordinary potential to enhance pragmatism by eliminating unnecessary elements and targeting multiple problems and populations, and to enhance predictive value by detecting mechanism engagement early in treatment. Community Mental Health Agencies (CMHAs), however, are often ill-equipped to use such measures of treatment quality due to burden and limited resources. Exposure therapy for anxiety is an ideal prototype for testing a practical, mechanism-informed quality measure in CMHAs given its potential for public health impact and clear theory of mechanism. The Exposure Guide (EG), a brief quality tool measuring therapist behaviors and mechanism, was developed based on microanalytic coded data showing a strong link between therapist behavior and patient outcome across three RCTs of exposure therapy in youth. Initial psychometrics for the EG using these RCT data are promising showing reliability, construct validity, and predictive validity, and pilot data suggests it may be acceptable and feasible in a community setting. Building upon these findings, we propose to test this novel measure of exposure quality, EG, in a community setting including its reliability and validity, its pragmatism, and which community end-users can become reliable and valid reporters. Therapists at a large local CMHA (N = 40) treating anxious youth and young adults ages 5-21 (N = 300) will participate in this study. The EG will be completed by 1) agency supervisors monthly, 2) therapists per session, 3) patient/families per session, and 4) study raters per session. Results from this study will establish an innovative model for measuring therapeutic elements that trigger mechanism of change in real-world therapy as well as inform future use of EG as a training tool to improve exposure quality in community settings.