Background: Safely liberalizing the diet to include an allergenic food may accelerate resolution of food allergy. The outcome of liberalization, however, varies among patients. Methods: We conducted a prospective observational study to identify factors associated with outcome for egg allergy 1 year after oral food challenge (OFC). We enrolled children < 72 months-old who had egg allergy and underwent OFC for determination of the safe intake quantity of egg allergen. At enrollment, each child’s clinical background was recorded. The Food Allergy Quality of Life Questionnaire–Parent Form (FAQLQ–PF) was administered to the caregivers to assess their children’s QoL. Dietary advice based on the OFC result was then provided to support safe consumption of eggs. At 1 year after OFC, the quantity of egg each child safely consumed in daily life was surveyed. We classified the egg allergy outcome as Outgrowing (Group O) if the quantity increased during the 1 year, or as Non-outgrowing (Group N) if it did not. Factors associated with the outcome were investigated by multivariate logistic regression analysis. Results: A total of 93 children were enrolled, and after 1 year 57 finished in Group O and 36 in Group N. The mean FAQLQ-PF score at baseline was significantly lower (i.e., better QoL) in group O than in group N. Multivariate logistic regression analysis identified comorbid asthma, comorbid atopic dermatitis and a poor QoL as factors predicting an unfavorable outcome. Conclusion: QoL may affect food allergy outcome. Intervention focusing on QoL may promote outgrowing food allergies.