Background Antibiotics are overused for non-pneumonia acute respiratory tract infections (ARTIs). Aim To establish prevalence and explore associations of delayed and immediate antibiotic prescribing strategies of Australian early-career GPs (specialist GP vocational trainees, also known as GP registrars) for non-pneumonia ARTIs. Design and setting Cross-sectional analysis of data collected between September 2016 and December 2017 from the Registrar Clinical Encounters in Training cohort (ReCEnT) study, an ongoing cohort study of GP registrars' in-practice clinical experiences in four Australian states and territories. Method Multinomial logistic regression with outcome antibiotic prescribing (no prescribing, immediate prescribing, and delayed prescribing). Results Of 7156 new ARTI diagnoses, no antibiotics were prescribed for 4892 (68%); antibiotics were prescribed for immediate use for 1614 diagnoses (23%) and delayed antibiotics were used for 650 diagnoses (9%). Delayed prescribing was used in 22% of otitis media, 16% of sinusitis, 13% of sore throat, 11% of acute bronchitis/bronchiolitis, and 5% of upper respiratory tract infection (URTI) diagnoses. Delayed prescribing was used for 29% of all prescriptions written. Delayed prescribing and immediate prescribing were associated with markers of clinical concern. Delayed prescribing was associated with longer duration of consultation and with fewer diagnoses/problems dealt with in the consultation. Conclusion Australian early-career GPs use no prescribing for ARTIs substantially more than established GPs; however, except where URTIs are concerned, they still prescribe antibiotics in excess of validated benchmarks. Australian early-career GPs may use delayed prescribing more often than European established GPs, and may use it to manage diagnostic uncertainty and, possibly, conflicting influences on prescribing behaviour. The use of delayed prescribing may enable a transition to an environment of more-rational antibiotic prescribing for ARTIs.