Researchers have been collecting data online since the early days of the Internet and as technology improves, increasing numbers of traditional experiments are being run online. However, there are still questions about the kinds of experiments that work online, particularly over experiments with time-sensitive performance measures. We are interested in one time-sensitive measure specifically, the time taken to resume a task following an interruption. We ran participants through an archetypal interruption study online and in the lab. Statistical comparisons showed no significant differences in the time it took to resume following an interruption. However, there were issues with data quality that stemmed from participant confusion about the task. Our findings have implications for experiments that assess time-sensitive performance measures in tasks that require continuous attention.