The kinetics of ferrite growth in three Fe–C–Mn–Si quaternary alloys has been measured using controlled decarburization tests at four temperatures between 755 C and 825 C, and a critical, quantitative test of the existence of a coupled solute drag effect (CSDE) is performed. The Mn and Si binding energies and trans-interface diffusivities (critical inputs in solute drag modelling) are taken directly from analogous experiments recently reported for ternary Fe–C–Mn and Fe–C–Si systems. The net solute drag effect experimentally observed in the quaternary system is found to be significantly less than that predicted by modelling using binding energies and trans-interface diffusivities calibrated on the respective ternary systems, i.e. an anti-CSDE is observed. This surprising observation is discussed in the context of solute interactions within the migrating interface and a number of future directions requiring investigation are highlighted.