Researchers are increasingly using web-based technologies to deliver family-based, prevention programming. Few studies have examined the success of such approaches for families with low incomes. The purpose of this study was to describe the level of in-class and online engagement in a childhood obesity prevention program for parents with low incomes, to examine the demographic correlates of parent engagement, and to examine dosage effects on parental feeding outcomes as a function of online exposure. All participants attended in-class nutrition education classes (Eating Smart ? Being Active) as part of the Expanded Food and Nutrition Education Program (EFNEP) in Colorado and Washington State (classes were offered in English and Spanish). Participants in this analysis were 168 parents from a larger cluster randomized controlled trial who had been randomly assigned to also receive a newly developed, mobile-based version of an efficacious, feeding-focused, childhood obesity prevention program. Results showed that despite high levels of in-person attendance (70%), participants only accessed 47% of the videos (online content). Older parents and parents of girls showed higher levels of in-person attendance; currently employed parents showed lower levels. Online engagement varied as a function of ethnicity and acculturation: non-Hispanic parents accessed the most videos, low-acculturated Hispanic parents accessed the second most, and highly acculturated Hispanic parents accessed the least. In contrast, low-acculturated Hispanic parents showed the highest in-person attendance. For all but one outcome, significant online program effects were found only for parents who accessed at least half of the videos. Implications for mobile-based, family-based prevention programs for parents with low incomes are considered.