Background. We aimed to determine the effect of dietary counseling or oral supplements on outcome for patients with cancer, specifically, nutritional outcome, morbidity, and quality of life (QOL), during and 3 months after radiotherapy. Methods. Seventy-five patients with head and neck cancer who were referred for radiotherapy (RT) were randomized to the following groups: group 1 (n = 25), patients who received dietary counseling with regular foods; group 2 (n = 25), patients who maintained usual diet plus supplements; and group 3 (n = 25), patients who maintained intake ad lib. Nutritional intake (determined by diet history) and status (determined by Ottery's Subjective Global Assessment), and QOL (determined by the European Organization for the Research and Treatment of Cancer Quality of Life Questionnaire version 3.0 [EORTC QLQ-C30]) were evaluated at baseline, at the end of RT, and at 3 months. Results. Energy intake after RT increased in both groups 1 and 2 (p ≤ .05). Protein intake also increased in both groups 1 and 2 (p ≤ .006). Both energy and protein intake decreased significantly in group 3 (p < .01 ). At 3 months, group 1 maintained intakes, whereas groups 2 and 3 returned to or below baseline levels. After RT, >90% of patients experienced RT toxicity; this was not significantly different between groups, with a trend for reduced symptomatology in group 1 versus group 2/group 3 (p < .07). At 3 months, the reduction of incidence/severity of grade 1+2 anorexia, nausea/vomiting, xerostomia, and dysgeusia was different: 90% of the patients improved in group 1 versus 67% in group 2 versus 51% in group 3 (p < .0001). After RT, QOL function scores improved (p < .003) proportionally with improved nutritional intake and status in group 1/group 2 (p < .05) and worsened in group 3 (p < .05); at 3 months, patients in group 1 maintained or improved overall QOL, whereas patients in groups 2 and 3 maintained or worsened overall QOL. Conclusions. During RT, nutritional interventions positively influenced outcomes, and counseling was of similar/higher benefit; in the medium term, only counseling exerted a significant impact on patient outcomes.