Develop and establish the reliability and validity of dietary behavior evaluation questions for the Expanded Food and Nutrition Education Program (EFNEP). A mixed-methods study using cognitive interviews, expert panels, test/retest reliability, and pretests/posttests. 14 states across the US. A convenience sample of low-income EFNEP or EFNEP-eligible participants for cognitive interviews (n = 111), reliability testing (n = 181), and sensitivity to change testing (n = 382). Indicators of face and content validity, temporal reliability, and sensitivity to change. Questions interpreted as intended in cognitive interviews, intraclass correlation coefficient and Spearman rank-order correlation for reliability testing; paired t tests or Wilcoxon signed-rank tests for sensitivity to change; and exploratory factor analyses to identify possible scales. Cognitive interviews resulted in 3 rounds of question revisions; reliability value ranges were 0.48–0.77 for intraclass correlation coefficient and 0.43–0.77 for Spearman rank-order correlation. For sensitivity to change, 9 items had evidence of change (P < 0.05) between pretests and posttests, whereas 5 items had evidence for change after removing those with little room to change. Two scales were identified: diet quality and non-cheese dairy. The EFNEP's new dietary behavior evaluation questions demonstrated face and content validity, moderate to strong reliability, and sensitivity to detect self-reported behavior changes among low-income, diverse populations (culturally, racially/ethnically, and level of education) across 14 states. Nutrition education programs targeting similar behaviors with English speaking clients could consider this dietary behavior questionnaire.