Abstract: Method, system and apparatus are disclosed for in-vessel composting of organic material. A compost handling apparatus moves forwardly through a bed of composting material in an elongate open bay. Specifically, an agitator comprises a feed belt such as a transversely mounted cylindrical drum, which feeds composting material to a conveyor which lifts the material and projects it rearwardly behind the agitator. A regulator, such as an adjustable deflector, controls the discharge of composting material by the conveyor. The deflector is adjusted as the agitator moves forward through the composting material to develop a level bed in the bay behind the agitator. A sensor may be employed to generate a depth signal corresponding to the depth of the composting material for controlling the deflector.