Numerous feeding strategies have been used to mitigate the catabolism of major burn injury. Whether higher energy and/or protein delivery results in better long-term outcomes is unknown. We performed a secondary analysis of data from adults with major burn injuries enrolled in the Randomized Trial of Enteral Glutamine to Minimize the Effects of Burn Injury at 54 burn centers in 18 countries. The sample was restricted to those who were mechanically ventilated within 72 hours of injury and for ≥7 days. Our key exposure was adequacy of energy, and protein ([Deliveredi/Prescribedi] × 100) was categorized into three groups each: low, 0% to 50%; moderate, ≥50% to 79%; and high, ≥80%. We also analyzed adequacy using restricted cubic splines. Primary and secondary outcomes included 6-month mortality and functional outcomes (i.e., 36-Item Short-Form Health Survey, Katz Index of Independence in Activities of Daily Living, Lawton Activities of Daily Living scores), respectively. Regression models were adjusted for age, body mass index, Charlson Comorbidity Index, baseline Acute Physiology and Chronic Health Evaluation II and modified Sequential Organ Failure Assessment scores, burn size, energy/protein adequacy, and study site. A total of 493 participants met the cohort restriction criteria; 336 participants were alive at 6 months. 36-Item Short-Form Health Survey, Katz Index of Independence in Activities of Daily Living, and Lawton Instrumental Activities of Daily Living Scale were completed by 218, 216, and 215 participants, respectively. The mean ± SD age was 48 ± 17 years, and 74% were male. The mean ± SD burn size was 41% ± 18% total body surface area. Participants who received 25% of recommended calories had nearly four times the hazard of death during the 6-month follow-up period than participants who received 100% of prescribed calories (adjusted hazard ratio, 3.89; 95% confidence interval, 1.35-11.20) (p = 0.02). There was no significant association between protein and 6-month mortality or energy/protein delivery and 6-month functional outcomes. There was a positive association between higher doses of energy and 6-month survival. This relationship conflicts somewhat with several energy studies among critically ill and non-burn-injured patients. The lack of consistent evidence on optimal nutrition for critically injured patients, a fundamental component of burn care, suggests potential for a randomized trial of lower versus higher energy to improve long-term outcomes after burn injury. Therapeutic/Care Management; Level III.