This study examined whether online tool support for regulation promotes student learning during collaborative inquiry in a computer simulation-based learning environment. Sixty-one students worked in small groups to conduct a scientific inquiry with fluid dynamics. Groups in the experimental condition received a support tool with regulatory guidelines; control groups were given a version of this tool from which these instructions were removed. Results showed facilitative effects for the fully specified support tool on learning outcomes and initial planning. Qualitative data elucidated how regulative guidelines enhanced learning and suggests ways to further improve regulative processes within collaborative inquiry learning settings.