The paper discusses the evaluation of a multistaged combustion burner design on a 0.6 MW package boiler simulator for in-furnace NOx control and high combustion efficiency. Both deep air staging, resulting in a three-stage configuration, and boiler front wall fuel staging of undoped natural gas, yielding four stoichiometric zones, reduced the baseline NO emission by about 50 percent to 160 ppm, meeting the program goal. However, deep air staging resulted in the entire front end of the boiler being fuel-rich and required penetrations into the boiler for staged air injection. The fuel staging results, on the other hand, required no boiler penetrations and only a small fuel-rich flame core in the boiler. Further, sufficient air for complete oxidation of the primary combustion products was provided at the burner exit, prior to staged fuel and air injection in the boiler, in the fuel staging tests.