The photoluminescence efficiency and linewidth are well-established metrics for characterizing potential laser active regions. We demonstrate the critical importance of a new parameter for predicting the performance of dilute-nitride lasers: the “optimal” postgrowth annealing temperature, defined as the annealing temperature giving the highest photoluminescence efficiency. We validate this assertion with two 1.55 μm edge-emitting GaInNAsSb lasers containing active regions with different optimal annealing temperatures. Although both active regions showed comparable photoluminescence efficiency and linewidth under optimal annealing conditions, laser performance was significantly different. The room-temperature threshold current density for the active region with higher optimal annealing temperature was 630 A/cm2, compared with 2380 A/cm2 for the sample with lower optimal annealing temperature. We conclude that overannealing of the gain region during upper cladding growth is the responsible mechanism. The dependence of the optimal annealing temperature on composition and growth conditions is also discussed.