How to Hide the Minimized Area

To hide the minimize area you can use the MinimizedAreaVisibility property and set its value to Collapsed.

<telerik:RadOutlookBar x:Name="RadOutlookBar1" MinimizedAreaVisibility="Collapsed"> 
    <telerik:RadOutlookBarItem Header="Item 1"> 
        <TextBlock Text="Item 1 Content" /> 
    </telerik:RadOutlookBarItem> 
    <telerik:RadOutlookBarItem Header="Item 2"> 
        <TextBlock Text="Item 2 Content" /> 
    </telerik:RadOutlookBarItem> 
    <telerik:RadOutlookBarItem Header="Item 3"> 
        <TextBlock Text="Item 3 Content" /> 
    </telerik:RadOutlookBarItem> 
</telerik:RadOutlookBar>