We developed a novel, unobtrusive estimate of team multitasking throughput (tMT). We demonstrate it through the quantitative assessment of tMT in distributed dyads when objective performance and purported reliability are manipulated among teammates. In a within-subjects experiment, we investigated the effects of teammates' performance and purported reliability on tMT. Results showed that when a teammate was described as reliable, there was a marked difference in tMT between those with low and high objective performance, but this difference was not present for teammates described as unreliable. Further, after considering the expected differences between high and low performing teams, we found partial support that tMT was highest when performance matched (vs. violated) expectation. These findings evidence the utility of our novel metric to capture team performance. In conclusion, we quantified how objective performance and purported reliability dynamically affect team efficiency while completing collaborative tasks. We found there was a marked difference in tMT between those with low and high purported reliability, but this difference was dependent on whether the teammate's performance matched expectations. (PsycInfo Database Record (c) 2024 APA, all rights reserved).