To evaluate the effectiveness of a critical thinking (CT) educational approach for Head Start parents in increasing offerings of dark green leafy, yellow/orange, cruciferous vegetables, tomatoes (specific vegetables), in their children’s diets. A two-group (experimental, control) randomized, pretest-posttest design was used. The experimental group participated in two 45-minute sessions on vegetables based on the CT approach. A CT definition, model, curriculum and lesson plans were developed. Significant differences were found between the experimental and control groups in mean posttest scores for vegetable knowledge 3.72 (SE 0.26) and 2.99 (SE 0.26), for critical thinking 2.34 (SE 0.63) and 0.73 (SE 0.47), and offerings of specific vegetables 6.11 (SE 0.48) and 4.97 (SE 0.45). There was no change in attitudes towards vegetables during the study. Participants already possessed positive attitudes before the intervention. Future work should continue the development of the critical thinking methodology.