Recent scholarship in comparative political behavior has begun to address how voters in coalitional systems manage the complexity of those environments. We contribute to this emerging literature by asking how voters update their perceptions of the policy positions of political parties that participate in coalition cabinets. In contrast to previous work on the sources of voter perceptions of party ideology in parliamentary systems, which has asked how voters respond to changes in party manifestos (i.e., promises), we argue that in updating their perceptions, voters will give more weight to observable actions than to promises. Further, coalition participation is an easily observed party action that voters use as a heuristic to infer the direction of policy change in the absence of detailed information about parties’ legislative records. Specifically, we propose that all voters should perceive parties in coalition cabinets as more ideologically similar, but that this tendency will be muted for more politically interested voters (who have greater access to countervailing messages from parties). Using an individual‐level data set constructed from 54 electoral surveys in 18 European countries, we find robust support for these propositions.