We investigated the microstructure and mechanical properties of (Zr_0.5Cu_0.4Al_0.1)_100−xTa_x (x=0–12) bulk metallic glass composites containing dispersed Ta-rich dendrites prepared by copper mold casting. With increasing Ta content, the volume fraction of the dendrite particle increases, while other crystalline phases are precipitated in the Ta content range of over 9 at%. The compressive fracture strength and plastic strain of the composites significantly increase from 1890 MPa and 0.7%, respectively, for the x=0 alloy to 2180 MPa and 15.9%, respectively, for x=9 alloy, and then significantly decrease with further increasing Ta content. The improvement of plasticity is attributed to an increase in the density of shear bands before final fracture resulting from the increase of the fracture strength.