Following injury, transfusion of red blood cells (RBCs) of increased storage duration has been associated with an increased morbidity and mortality. Prospective trials focusing on the impact of the storage age of RBCs in severely bleeding trauma patients have failed to accrue patients. This has been attributed to an inability to maintain a large inventory of fresh RBCs, and the difficulties in obtaining consent in severely bleeding trauma patients. To address these issues, we performed a prospective, observational pilot study to evaluate the feasibility of conducting a trial focusing on RBC age in patients following injury. Methods Patients with bleeding due to trauma were transfused RBCs ≤10 day old if they were ABO blood Type O (Group O) or were transfused the oldest RBCs in inventory if they were Type A, B or AB (Group A/B/AB). Clinicians were unaware of the specific age of the RBCs. Results 63 patients were analyzed (Group O, n = 19; Group A/B/AB, n = 44). Half of all patients had severe injuries ISS (median 22). The median admission base deficit was -5 mEq/L, and median total 24 h use of RBC and FFP was 1.2 L. The age of RBCs transfused to Group O was significantly lower than for Group A/B/AB [median (IQR) A/B/AB = 18.4 (11.4-25.4) days, and Group O = 6 (4.2-7.8) days; p < 0.001]. Conclusions It appears feasible to conduct a RBC age trial in trauma patients using ABO blood type to construct comparative groups. Adequate RBC age separation between cohorts and reduced RBC age in the "young" group of patients who received units ≤10 days old was achieved.