Background: Open long-bone fractures represent a complex injury within the trauma system. Guidelines recommend antibiotics be given within 60 minutes of patient arrival to the emergency department. We sought to measure and improve the timeliness of antibiotic administration at the patient, hospital, and population level within a collaborative quality initiative. Methods: Trauma collaborative quality initiative data (January 2017 to December 2020) were analyzed from 34 American College of Surgeons Committee on Trauma verified level 1 and level 2 trauma centers. Inclusion criteria were adult patients (≥16 years), injury severity score ≥5, and open tibia or femur fracture. After the baseline year, hospitals were scored annually on a pay-for-performance metric based on patients receiving antibiotics within 120 minutes of emergency department arrival. Univariate tests examined the differences between baseline and subsequent year(s) performance. A multivariable logistic regression assessed the factors associated with meeting this target time. Results: There were 2,624 patients with an open long-bone fracture. In the baseline year (2017), 76.9% of patients received antibiotics in ≤120 minutes, with a mean time of 57.9 ± 63.3 minutes. After implementing collaborative quality initiative–wide targets, performance significantly improved in subsequent years (2018, 2019, 2020). The collaborative quality initiative achieved their goal of ≥85% of patients receiving antibiotics in ≤120 minutes in 2019 (87.9%) and 2020 (88.5%), with a mean time of 43.3 ± 54.8 minutes (P < .05 vs 2017). Conclusion: A pay-for-performance process measure within a statewide trauma collaborative quality initiative improved the timely administration of antibiotics to patients with open fractures. Work remains to align compliance with the guideline target of <60 minutes and to identify factors involved in the delay of administration.