The Observational System for Recording Physical Activity in Children (OSRAC-P, Brown et al., 2009) is a discontinuous measurement system for recording physical activity. We validated the OSRAC system with continuous measurement systems (pedometers and heart rate monitors), finding that increased heart rate and steps taken correlated with activity level codes. We also measured changes in physical activity in obese and overweight pre-school children when a package intervention including goal setting and feedback was introduced according to an ABAB reversal design. Multiple measures were used to assess physical activity level, including the OSRAC-P system and pedometers. Percentile schedules of reinforcement were used to set performance goals. The intervention produced elevated levels of physical activity and the activity level codes and pedometer records were highly correlated. Implications for future activity research will be discussed.