Scope A major downside of oral immunotherapy (OIT) for food allergy is the risk of severe side effects. Non‐digestible short‐ and long‐chain fructo‐oligosaccharides (scFOS/lcFOS) reduce allergy development in murine models. Therefore, it is hypothesized that scFOS/lcFOS can also support the efficacy of OIT in a peanut allergy model. Methods and Results After sensitization to peanut extract (PE) using cholera toxin, C3H/HeOuJ mice are fed a 1% scFOS/lcFOS or control diet and receive OIT (1.5 or 15 mg PE). Hereafter, mice are exposed to PE via different routes to determine the safety and efficacy of treatment in clinical outcomes, PE‐specific antibody production, and numbers of various immune cells. scFOS/lcFOS increases short‐chain fatty acid levels in the caecum and reduce the acute allergic skin response and drop in body temperature after PE exposure. Interestingly, 15 mg and 1.5 mg OIT with scFOS/lcFOS induce protection against anaphylaxis, whereas 1.5 mg OIT alone does not. OIT, with or without scFOS/lcFOS, induces PE‐specific immunoglobulin (Ig) IgG and IgA levels and increases CD103+ dendritic cells in the mesenteric lymph nodes. Conclusions scFOS/lcFOS and scFOS/lcFOS combined with low dose OIT are able to protect against a peanut‐allergic anaphylactic response. A major downside of oral immunotherapy (OIT) for food allergy is the risk of side effects. Dietary supplementation with nondigestible short‐ and long‐chain fructo‐oligosaccharides (scFOS/lcFOS) (FF), after peanut allergy development, is shown to reduce the allergic reaction upon peanut exposure. Interestingly, a high dose of OIT and low dose OIT combined with FF also induced protection against an allergic reaction, whereas low dose OIT alone did not. This suggests that combining OIT with FF enables the use of a lower dose of OIT.