The use of electrorheological (ER) materials in adaptive structures has received much attention. Adaptive structures are based on controlling the pre-yield rheology of ER materials, which is achieved by applying different electrical fields. In this study the dynamic behavior of an ER material based adaptive beam was modeled. The beam was composed to three layers: an ER material controllable damping layer and surrounding upper and lower elastic plates. The structural model of the assembly in a transverse continuous vibration mode subjected to simply-supported boundary conditions and actuation at a single point on the adaptive beam surface was analysed. The model was tested under the conditions of varying forcing frequency from 0-300 Hz, and applied electrical field from 0-35 kV mm-1. The analytical results are compared with experimental results under the same physical conditions. Qualitative agreement between theory and experimentation resulted. In addition an effect was made to reduce the vibration of the structure by selecting the optimum electrical field which yields minimized vibration for each frequency. Continuing efforts towards further understanding the behavior of ER material based adaptive structures are discussed.