The United States is currently experiencing an opioid abuse epidemic. Many policies and programs have been implemented at local, state, and national levels in an attempt to decrease prescription opioid addiction and overdose. On August 1, 2014, Colorado Medicaid implemented a policy change that limited the quantity of short-acting opioids (SAOs) that could be filled through the Medicaid benefit to no more than 4 tablets per day, or 120 tablets in 30 days. To compare mean total daily dose (TDD) of opioids purchased by Kaiser Permanente Colorado (KPCO) Medicaid patients before and after implementation of the Medicaid SAO quantity limit. This investigation used a pre/post study design to compare opioid use in Medicaid-eligible patients during the 90 days before implementation of the Medicaid quantity limit on August 1, 2014, and 90 days after full implementation of the change on December 31, 2014. The study was conducted at KPCO, an integrated care delivery system providing medical care for approximately 615,000 patients, of which over 54,000 are Medicaid members. Electronic medical and pharmacy records were used to identify patients and assess medication use. There was a small difference in opioid use in the population of Medicaid opioid users as evidenced by the median TDD of oral morphine equivalents (OME) purchased decreasing from 6.8 mg (IQR = 2.2-25.8) in the pre-implementation period to 6.6 mg (IQR = 1.7-24.0) in the postimplementation period (P = 0.027). The proportion of patients purchasing more than 120 mg OME per day and the proportion of patients purchasing long-acting opioids (LAOs) did not change significantly from the pre- to postimplementation period (OME > 120 of 4.2% vs. 3.6%, respectively, P = 0.290; LAO use of 12.9% vs. 13.6%, respectively, P = 0.465). This study found a statistically significant 3% decrease of 0.2 mg OME per day in the primary study population. A 24% reduction of 10 mg OME per day before and after implementation of the Medicaid SAO quantity limit was found in those patients identified as exceeding the Medicaid SAO quantity limit at baseline. These patients tended to be purchasing low to moderate total daily doses of opioids at baseline. Internal funding was provided by the Department of Pharmacy at Kaiser Permanente Colorado. There are no external funding sources to disclose. Riggs, Milchak, Patel, and Heilmann are employed by Kaiser Permanente Colorado. The authors report no other potential conflicts of interest. Study concept and design were contributed by Riggs, Heilmann, and Billups, along with the other authors. Billups collected the data, and data interpretation was performed by Riggs, Milchak, and Flores, with assistance from the other authors. The manuscript was written primarily by Riggs, along with Flores, and revised by Billups, Milchak, Patel, and Heilmann.