A grain treatment system (10) incorporating a steam vessel (12) and centrally disposed, grain diverting steam sparger unit (90) for facilitating the flow of homogeneous plugs of grain therearound. The system incorporates a discharge unit (18) having garner valves (75, 77) and/or flow restrictors for facilitating the anti-coring grain flow through the steam vessel (12) with side and corner draw-off therein and the even percolation of steam upwardly therethrough for uniformly heating and moisturizing the grain. A vapor generator (15) is used for providing a heating medium comprising a mixture of condensible and non-condensible gases introduced into the grain through the centrally disposed steam sparger (90). In this manner, homogeneous plugs of grain are uniformly passed through and discharged from the grain treatment system permitting controlled heating and moisturizing of grain and substantially eliminating of coring, grain clingage, static sludge build-up and associated grain treatment problems prevalent in the many prior art systems.