Synthesis of effects of infant feeding interventions to prevent childhood obesity is limited by outcome measurement and reporting heterogeneity. Core outcome sets (COSs) represent standardised approaches to outcome selection and reporting. The aim of this review is to identify feeding outcomes used in infant feeding studies to inform an infant feeding COS for obesity prevention interventions. The databases EMBASE, Medline, CINAHL, CENTRAL, and PsycINFO searched from inception to February 2017. Studies eligible for inclusion must examine any infant feeding outcome in children ≤1 year. Feeding outcomes include those measured using self-report and/or observational methods and include dietary intake, parent–child interaction, and parental beliefs, among others. Data were extracted using a standardised data extraction form. Outcomes were assigned to outcome domains using an inductive, iterative process with a multidisciplinary team. We identified 82 unique outcomes, representing nine outcome domains. Outcome domains were “breast and formula feeding,” “introduction of solids,” “parent feeding practices and styles,” “parent knowledge and beliefs,” “practical feeding,” “food environment,” “dietary intake,” “perceptions of infant behaviour and preferences,” and “child weight outcomes.” Heterogeneity in definition and frequency of outcomes was noted in reviewed studies. “Introduction of solids” (59.5%) and “breastfeeding duration” (55.5%) were the most frequently reported outcomes. Infant feeding studies focus predominantly on consumption of milks and solids and infant weight. Less focus is given to modifiable parental and environmental factors. An infant feeding COS can minimise heterogeneity in selection and reporting of infant feeding outcomes for childhood obesity prevention interventions.