We anesthetized 301 bridled nailtail wallabies (Onychogalea fraenata), captured within Scotia Sanctuary, New South Wales, Australia over four nights in October 2009 to perform health assessments before their release into a predator-proof exclosure. We tested two anesthetic dose-rate combinations, protocol 1 (0.08 mg/kg medetomidine–4.5 mg/kg ketamine), and protocol 2 (0.1 mg/kg medetomidine–5 mg/kg ketamine), each given intramuscularly. Median time from injection to recumbency for protocol 1 was 10 min (1–27 min) and for protocol 2 was 12 min (2–28) (P = 0.12). Five animals died during the induction with protocol 2; none died with protocol 1 (P = 0.06). Physiologic parameters were recorded during recumbency, with no significant abnormalities with protocol 1. Protocol 1 was an effective, efficient regime to anesthetize large numbers of bridled nailtail wallabies under field conditions.