The Environmental Rating Scale (ERS) is the only autism spectrum disorders (ASD) specific tool for assessment of residential services and treatment models. However, one limitation with the ERS is its dependence on expert observations and interviews, particularly in larger scale studies. The ERS has therefore been adapted into a staff self-report questionnaire (ERS-Q). Here the measurement properties of the ERS-Q were examined according to traditional test theory criteria. Data provided support for summation of raw item scores into total and subscale ERS-Q scores and item-total correlations indicated that items within scales tap a common construct, suggesting that the ERS-Q is useful in survey as well as interventional studies. As such the ERS-Q appears a valuable addition to the current ASD research toolbox. The Environmental Rating Scale (ERS) is the only autism spectrum disorders (ASD) specific tool for assessment of residential services and treatment models. However, one limitation with the ERS is its dependence on expert observations and interviews, particularly in larger scale studies. The ERS has therefore been adapted into a staff self-report questionnaire (ERS-Q). Here the measurement properties of the ERS-Q were examined according to traditional test theory criteria. Data provided support for summation of raw item scores into total and subscale ERS-Q scores and item-total correlations indicated that items within scales tap a common construct, suggesting that the ERS-Q is useful in survey as well as interventional studies. As such the ERS-Q appears a valuable addition to the current ASD research toolbox.