In this experimental study, gasification characteristics of Indian coals having high ash content (>35%) in a bubbling fluidized bed reactor, using air and steam as the gasification agents under atmospheric pressure, are presented. The thermal power output of the gasification device has been varied in the range of 80–100 kW. The ratio of the actual mass flow rate of air supplied to the stoichiometric air mass flow rate (required for complete combustion) has been varied in the range of 0.25–0.35. The ratio of mass flow rate of steam to that of coal has been varied from 0.15 to 0.25. Effects of air and steam flow rates on the calorific value of product gas, carbon conversion and cold gas efficiency have been studied in detail. For high-ash Indian coals, supply of steam produces positive effect as all the metrics such as calorific value of product gas, carbon conversion and cold gas efficiency increases with increase in the steam supply rate. © 2017 Elsevier Ltd