I found .hasClass on the ParametersArea div to be a more reliable way of checking. I kept getting inconsistent results back with the .checked() on the command object.
$("#reportViewer1") .telerik_ReportViewer({ serviceUrl: "/api/reports/", viewMode: "INTERACTIVE", scaleMode: "SPECIFIC", reportSource: { report: reportClass, parameters: { CultureID: "en" } }, renderingEnd: function() { if($("div[data-role$='_ParametersArea']").hasClass("hidden")) this.commands.toggleParametersArea.exec(); } });