Mutation of theDrosophila melanogasterGluRIIAgene or pharmacological agents targeting it are commonly used to assess homeostatic synaptic function at the larval neuromuscular junction (NMJ). The commonly used mutation,GluRIIASP16, is a null allele created by a large and imprecise excision of a P-element which affectsGluRIIAand multiple upstream genes. Here we mapped the exact bounds of theGluRIIASP16allele, refined a multiplex PCR strategy for positive identification ofGluRIIASP16in homozygous or heterozygous backgrounds, and sequenced and characterized three new CRISPR-generatedGluRIIAmutants. We found the three newGluRIIAalleles are apparent nulls that lack GluRIIA immunofluorescence signal at the 3rdinstar larval NMJ and are predicted to cause premature truncations at the genetic level. Further, these new mutants have similar electrophysiological outcomes asGluRIIASP16, including reduced miniature excitatory postsynaptic potential (mEPSP) amplitude and frequency compared to controls, and they express robust homeostatic compensation as evidenced by normal excitatory postsynaptic potential (EPSP) amplitude and elevated quantal content. These findings and new tools extend the capacity of theD. melanogasterNMJ for assessment of synaptic function.