Food insecurity acts as a chronic stressor independent of poverty. Food-insecure adults may consume more highly palatable foods as a coping mechanism, leading to poorer diet quality and increased risks of chronic disease over time. Using data from the 1999-2008 National Health and Nutrition Examination Surveys, this study aimed to examine the cross-sectional differences in dietary intake and diet quality by household food security among 8,129 lower-income adults (≤300% of the federal poverty level). Food insecurity was assessed using the 18-item US Household Food Security Survey Module. Dietary intake was assessed from 24-hour recalls and diet quality was measured using the Healthy Eating Index-2005 and the Alternate Healthy Eating Index-2010. Relative mean differences in dietary outcomes by household food security were estimated using linear regression models, adjusting for sociodemographic characteristics. Lower-income food-insecure adults reported higher consumption of some highly palatable foods, including high-fat dairy products (P trend<0.0001) and salty snacks (P trend=0.01) compared with lower-income food-secure adults. Food insecurity was also associated with more sugar-sweetened beverages (P trend=0.003); more red/processed meat (P trend=0.005); more nuts, seeds, and legumes (P trend=0.0006); fewer vegetables (P trend<0.0001); and fewer sweets and bakery desserts (P trend=0.0002). No differences were observed for intakes of total energy and macronutrients. Food insecurity was significantly associated with lower Healthy Eating Index-2005 (P trend<0.0001) and Alternate Healthy Eating Index-2010 scores (P trend<0.0001). Despite no macronutrient differences, food insecurity was associated with characteristics of poor diet quality known to increase chronic disease risk.