The glass forming ability(GFA) and thermodynamic properties of the La-Al-Cu-Co alloy system were investigated, and novel La-Al-Cu-Co bulk metallic glasses(BMGs) with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-Al-Cu-Co alloys was well-correlated with the supercooled liquid region, ΔT x, and the parameter, γ; but not with the reduced glass transition temperature, T rg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be used in various applications. The GFA of the present alloys exhibited a dependence on the relative number of Al–Co and Al–Cu atomic pairs, i.e., on the Al:Co and Al:Cu ratios, which were ~2.3 and 0.85, respectively. The glass forming ability (GFA) and thermodynamic properties of the La-Al-Cu-Co alloy system were investigated, and novel La-Al-Cu-Co bulk metallic glasses (BMGs) with a minimum critical diameter of 8 mm were fabricated. The differing GFAs were examined from a thermodynamic viewpoint. The GFA of the La-Al-Cu-Co alloys was well-correlated with the supercooled liquid region, ΔT x, and the parameter, γ; but not with the reduced glass transition temperature, T rg. In addition, the La62Al14Cu14Co8 BMG exhibited a high GFA, low glass transition temperature of 412 K, and a broad supercooled liquid region of 70 K. These novel BMGs, which were fabricated from low-cost raw materials, had the potential to be The GFA of the present alloys exhibits a dependence on the relative number of Al-Co and Al-Cu atomic pairs, ie, on the Al: Co and Al: Cu ratios, which were ~ 2.3 and 0.85, respectively .