An improved seed metering wheel assembly is provided to deliver a substantially constant flow of seed to a downstream treating device or the like, without any substantial surging of seeds. The seed metering wheel assembly includes an axially rotatable metering wheel having a plurality of strategically sized and arranged seed metering openings therethrough, arranged in circular arrays of differently sized metering openings. In another embodiment, the seed metering wheel includes a central hub section and an outermost rib, with a series of ribs between the hub section and rim, which lie along respective non-diameter chords. Incoming seed is delivered from a seed hopper outlet by gravitation to the metering wheel, which preferably provides a substantially constant open area while preventing wholly unobstructed flow of seeds.