After head and neck cancer (HNC) treatment, dysgeusia may be a barrier to oral intake. In this exploratory study, we prospectively examined taste perception, clinician-rated (CRO) and patient-reported (PRO) taste changes and their effect on oral intake postradiotherapy. Twenty-eight patients were assessed at baseline, treatment weeks 2 and 4, and 1, 3, and 6months post-treatment using a whole-mouth taste test and associated CRO and subjective PRO measures. Greater taste impairment was reflected by subjective than by a whole-mouth taste test. The most significant and consistent decline occurred mid-treatment. The Chemotherapy-Induced Taste Alteration Scale (PRO) discomfort subscale correlated significantly with maintaining an oral diet, percent of oral intake, and appetite level from mid-treatment to 6months post-treatment. PRO results indicated ongoing oral intake issues. Whole-mouth taste tests may fail to fully reflect functional taste-loss. Dysgeusia prevention and treatment methods are needed to improve patient outcomes.