A slide valve assembly is provided for selectively dispensing dry goods from a hopper. The slide valve assembly is readily attached and detached from the hopper and is readily disassembled and reassembled to facilitate cleaning and/or servicing. Preferably, the slide valve assembly includes a panel secured to spaced support rails, a movable valve panel for opening and closing of the dispensing portion of the hopper, and a collar retainer for releasable attachment to the dispensing portion of a hopper. The slide valve assembly may be attached, detached, assembled, and disassembled substantially without the use of tools or separate fasteners, to minimize the risk of creating a contamination hazard for the goods dispensed from the hopper, while still allowing for secure attachment to the hopper.