We report on in-plane magnetic anisotropy in epitaxial bcc Co/Fe(110) bilayers on W(110). The magnetic surface anisotropy in the Co/Fe(110) bilayers exhibited a strong nonmonotonic dependence on Co coverage. Magneto-optical studies revealed a sharp maximum of the magnetic surface anisotropy, 2.44 mJ/m 2 , at d Co = 5Å. This giant interfacial magnetic anisotropy allowed a small fraction of a Co monolayer to reorient the magnetization of the bulk-like Fe film. We conclude that the mono-and double-layer bcc Co(110) exhibited in-plane magnetic anisotropy with a [110] easy axis.