In the yeast Saccharomyces cerevisiae, cells undergoing sporulation form prospore membranes to surround their meiotic nuclei. The prospore membranes ultimately become the plasma membranes of the new cells. The putative phospholipase Spo1 and the tandem Pleckstrin Homology domain protein Spo71 have previously been shown to be required for prospore membrane development, along with the constitutively expressed Vps13 involved in vacuolar sorting. Here, we utilize genetic analysis, and find that SPO73 is required for proper prospore membrane shape and, like SPO71, is necessary for prospore membrane elongation. Additionally, similar to SPO71, loss of SPO73 partially suppresses spo1Δ. Spo73 localizes to prospore membranes and complexes with Spo71. We also find that phosphatidylserine localizes to the prospore membrane. Our results suggest a model where SPO71 and SPO73 act in opposition to SPO1 to form and elongate prospore membranes, while VPS13 plays a distinct role in prospore membrane development.