In the context of the obesity epidemic, understanding environmental influences on eating patterns is critical. This study examined the effects of one built and one social environmental feature on three eating behaviors during a buffet-style meal: number of serving trips, amount of food and beverage served (grams and calories), and amount of food and beverage consumed (grams and calories). The within-subjects independent variable, kitchen floor plan openness, had two levels (open and closed) which were manipulated by placing folding screens in a test kitchen with open floor plan (where food and external eating cues were more salient) to convert it into a "closed" kitchen with no view of kitchen appliances, counters, or food. The between -subjects independent variable, social familiarity, was operationalized by participant dining group composition: friends versus strangers. A repeated measures, 2x2 factorial study was conducted with 57 college students in a test kitchen. Statistical analyses were conducted using a linear mixed model procedure to examine both main effects of and interactions between kitchen floor plan openness and social familiarity on three eating behavi ors, as well as how these effects were moderated by education level, gender, hunger, social interaction, ethnicity, income, housing type, age, BMI, dining group size, serving trips (dependent variable: amount served), and amount served (dependent variable: amount consumed). All predictors, except for ethnicity, income, housing type, and age, were significant in at least one model. Findings suggested that dining in the open condition was associated with an increase in serving trips, but effects were moderate d by main effects of and various interactions between social familiarity, education level, gender, social interaction, BMI, and dining group size. Dining with strangers was also associated with an increase in serving trips and amount consumed (grams), but effects were moderated by main effects of and some interactions between education level, gender, social interaction, dining group size, and amount served. Findings suggested that floor plan openness influenced serving trips, and social familiarity affected serving trips and amount consumed. Study strengths, limitations, and suggestions for future work are also discussed.