In this study, the semi-active vibration control capabilities of electrorheological (ER) material based axially non-homogeneous adaptive beams were investigated. The adaptive nature of such beams was achieved by controlling the pre-yield rheology of ER material in response to varying applied electric field levels. The beams focused on were designed in a way that can allow for independent control of the electric field levels applied to four sections of the beam. The cross-sectional configuration was based on sandwiching of the ER material between the elastic faceplates. Controllability of the four sections was achieved by selectively coating electrically non-conductive elastic faceplates with a conductive material. Narrow insulated regions were left between adjacent adaptive sections. A vibration model was developed based on thin-plate theory, and the transverse continuous vibration response of the non-homogeneous ER adaptive beam was studied. The developed model was applied to each region of the axially non-homogeneous beam separately. Continuity in the response of the overall structure was achieved by appropriate coupling of the adjacent regions. The resulting analytical model was able to predict the structural vibration response in the forms of natural frequencies, mode shapes, loss factors and the transverse vibration response at any location on the beam surface as functions of excitation frequency and applied electric field levels. Vibration control capacity of the ER adaptive beam was illustrated by emphasizing mode shape control. The structure was subjected to on and off position electric field configurations at each section. The `on' state was defined as an applied electric field of 3.5 kV and the `off' state was actually 0.5 kV . Based on the on/off conditions at each section, various electric configurations were selected for the overall adaptive beam. Variations in the mode shape amplitude and geometry were studied for the selected electric field configurations. Natural frequencies and loss factors of the structure were predicted for each configuration. Controllability of the non-homogeneous ER adaptive beam was observed.