<p>Parallelizing monodisperse microbubble generators within microfluidic devices offers a promising strategy for significantly increasing production throughput. However, gases differ fundamentally from liquids in key properties—such as low viscosity and density, high interfacial tension with liquids, and high compressibility—complicating the uniform generation of bubbles across multiple generators. These gas-phase characteristics introduce coupling effects between parallel units and result in hydrodynamic feedback from the collection channels, making scalable operation more challenging. In microfluidic systems, gas and liquid enter the bubble-generation channels as single-phase flows. After bubble formation, two-phase flow resistance dominates in the collection channels. Therefore, this study aims to investigate the uniformity of bubbles produced by eight parallel flow-focusing generators under two-phase flow conditions. The influence of gas pressure, capillary number, and viscosity ratio is examined experimentally. We find that achieving uniform fluid distribution for monodisperse bubble generation requires consideration of additional two-phase hydrodynamic resistance, determined by both the capillary number and viscosity ratio. This study addresses a critical gap in understanding two-phase flow resistance and provides design guidelines for the scalable production of uniform bubbles.</p>