Increased food intake in Zucker obese rats has been reported as early as 16 days of age. To determine if the feeding behavior of Zucker obese rats differs from that of lean rats by weaning, or if the differences develop with age, feeding patterns of Zucker obese and lean rats were compared from 3–10 weeks of age. Increased food intakes of obese rats at 3 weeks of age were due to a trend toward increased frequency while at 4 weeks of age were due to increased meal size. Meal size subsequently increased at a faster rate in obese than lean rats and meal frequencies did not differ. While always greater in obese than lean rats meal durations decreased and rates of eating increased with age and were not different for obese and lean rats. The adult patterns of diurnal variation in obese and lean rats were apparent by 3 weeks of age. Thus, in the Zucker obese rat the characteristic of increased meal size did not occur until 4 weeks of age after increased food intake and body weight were evident, and the characteristic of decreased meal frequency did not occur by 10 weeks of age. While increased meal size is associated with early differences in feeding behaviors, decreased meal frequency may be a consequence of obesity.