Importance: Misuse and overselling of over-the-counter pharmaceuticals poses a major burden on both private and public health expenditures. Objective: To seek evidence on whether over-the-counter medication dispensing behavior complies or conflicts with the protocols indicated in practice standards and guidelines of a national professional pharmacy organization. Design, Setting, and Participants: This quality improvement study was undertaken in 205 pharmacies in the wider Brisbane, Australia, area. Two standardized patient (SP) scenarios were developed to evaluate noncompliant behavior. Data collection for scenario 1 was conducted between November 23 and December 9, 2016. Data collection for scenario 2 was conducted between September 1 and 28, 2017. A 2-sample test of proportions and a probit regression model were used to evaluate the likelihood of noncompliant treatments and overtreatments in each case scenario. Statistical analysis was performed from January 30 to June 21, 2018, and revised in May 2019. Main Outcomes and Measures: Outcomes were the observed likelihood of noncompliant treatments and overtreatments. Noncompliance is defined as treatments not complying with practice standards and guidelines set by the professional pharmacy society. Noncompliant treatments include undertreatment (patient did not receive necessary treatment) and overtreatments (patient was supplied with more than sufficient treatments) in both scenarios. Results: In scenario 1, 9 trained female SPs visited 89 pharmacies to request emergency hormonal contraception from pharmacy staff. In 45 cases, SPs reported having unprotected intercourse within the last 24 hours (case 1A), and in 44 cases, SPs reported having unprotected intercourse more than 72 hours ago (case 1B), which is past the efficacy threshold of over-the-counter emergency hormonal contraception. In scenario 2, 11 SPs (5 male and 6 female) visited 150 pharmacies (154 visits in total) to request treatment for family members or a partner with symptoms indicating bacterial conjunctivitis (case 2A; n = 73) or viral conjunctivitis (case 2B; n = 81). In scenario 1-dispensing emergency hormonal contraception when physician referral is recommended-21 of 44 pharmacists (47.7%) in case 1B violated the recommendation by selling the over-the-counter medication. With the inclusion of both no physician referral and emergency hormonal contraception sold, this rate increased to 79.5% (35 of 44 pharmacists). In scenario 2-1 case each of bacterial and viral conjunctivitis-overtreatment occurred in 55 of 154 cases (35.7%). In both scenarios, 140 of 243 pharmacies (57.6%) followed dispensing behavior compliant with the protocol, while 76 of 243 pharmacies (31.3%) involved some form of overtreatment or overselling of medication. Some evidence of an association between sex of SP and pharmacist was also found. Conclusions and Relevance: Although the market for dispensing over-the-counter medication in Australia is regulated, relatively high rates of overtreatment and some cases of undertreatment were observed in this study. Given the unintended adverse effects, including overuse of antibiotics and corticosteroids, these observations suggest the advisability of regulatory intervention ensuring compliance with professional protocols..