Plasmonic nanoparticles (NPs) arranged into assemblies can manipulate near-field profiles and modify far-field characteristics compared to a single NP. The ability to tune each nanoparticle in a plasmonic assembly can reveal new architectures for plasmon-enhanced applications. We developed a nanofabrication approach, Reconstructable Mask Lithography (RML), to achieve independent control over the size, position, and material of up to four nanoparticles within a subwavelength unit as well as produce these nanostructures over large areas (cm2) into ordered arrays. Au-Pd assemblies fabricated by RML displayed high sensitivity, fast response times, and excellent recovery in detecting both high and low concentrations of hydrogen gas. Our results suggest that arrays of plasmonic hetero-oligomers consisting of strong plasmonic materials and reactant-specific elements provide a unique platform for plasmon-enhanced applications and pave the way toward integration of multi-functions within deep sub-wavelength footprints.