It has been found that alloying with Cu element could significantly enhance the glass-forming ability (GFA) of Ti-Zr-Be-Fe alloy. As a result, a series of centimeter-scale (Ti41Zr25Be28Fe6)(100-x)Cu-x (x = 0 -20 at.%) bulk metallic glasses (BMGs) have been developed. Especially for those with x = 7-13 at.% Cu content, the critical size is larger than 20 mm. Among these Ti-based BMGs, (Ti41Zr25Be28Fe6)(91)Cu-9 (also noted as Ti37.31Zr22.75Be25.48Fe5.46Cu9) glassy alloy exhibits superior GFA with a critical size larger than 32 mm, which is the largest size of Ti-based BMGs ever reported so far. The enhancement of the GFA is suggested to arise from the Cu addition-induced decrease in both the liquidus temperature and the Gibbs energy difference between the undercooled liquid and the crystalline phases of Ti-Zr-Be-Fe alloy. In addition to its superior GFA, the lightweight (Ti41Zr25Be28Fe6)(91)Cu-9 alloy also exhibits a remarkable high specific strength of 3.7 x 10(5) N m kg(-1) and an apparent plastic strain of 1.2%.