Amorphous ribbons of (Fe1-xCox)88Zr7B4Cu1 (x = 0.2, 0.35, 0.5, and 0.6) alloys were annealed to produce a nanocrystalline phase dispersed in the amorphous matrix. Precision lattice parameter calculation showed that composition of the nanocrystalline phase is Fe73Co27 for all the alloys irrespective of initial alloy composition. This result was well corroborated with the Mössbauer results. Saturation magnetization of annealed ribbons was almost same for all the alloys, however, coercivity increases with Co content.