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In this work, we propose a simple approach for designing plastic bulk metallic glasses (BMGs) by exploiting the ductility of intermetallic compounds involved in the BMG-forming system. Its validity was examined by investigating a series of quaternary CuZr-Y-Al alloys along the composition tie-line between Cu(42)Zr(44.4)Y(3.6)Al(10) (Y1) and the B2 CuZr phase, expressed as (Cu(0.5)Zr(0.5))(x)(M)(100-x) (M = Zr(0.15)Y(0.225)Al(0.625), 84 <= x <= 93). When tuning the composition towards the CuZr, the glass-forming ability of alloys is dramatically degraded, showing a reduction of critical diameter D(c) for BMG formation from 16 mm at x = 84 (Y1) to 2 mm at x = 93. As the composition of BMGs shifts to the CuZr terminal, the shear modulus mu of the BMGs decreases, whereas the Poisson's ratio nu increases. With respect to the Y1 BMG, compressive plasticity and toughness of the Y2 BMG (x = 92, D(c) = 4 mm) with a higher concentration of the CuZr are improved, which is consistent with its lower mu and higher nu values.