Combustion of gaseous fuel in meso-scale ducts with backward facing step was studied experimentally. Premixed mixture of methane-air has been used as a fuel for the experiments. The effect of change in step-height, mixture equivalence ratio and flow rates on stability limits of flame and flame position are investigated. The corresponding regime plots were drawn highlighting the regions where flame was anchored within the duct. It was found that with an increase in step-height, the tendency for the flame to travel upstream increases. It was also observed that the flame displayed certain unstable characteristics in the form of oscillations which lead to the extinction of the flame.