The current study was designed to evaluate a rotating momentary time sampling (MTS) data collection system. A rotating MTS system has been used to measure activity preferences of preschoolers but not to collect data on responses that vary in duration and frequency (e.g., talking). We collected data on talking for 10 preschoolers using a 5-s MTS and interpolated larger MTS values. Results indicated that 30-, 60-, and 90-s intervals approximated the 5-s MTS. Next, we implemented a rotating MTS for each value in which we observed either 10 or 19 students. For all interval durations, there was high interval-by-interval interobserver agreement (IOA). However, we found overall low occurrence IOA. These results illustrate that it is important to consider which IOA algorithm is used, based on the type of data collected.