We report the device characteristics of stacked InAs/GaAs quantum dots (QDs) with GaP strain-compensation (SC) layers grown by metal organic chemical vapor deposition. By inserting GaP SC layers within the stacked structures, decrease in the density of QDs by stacking QDs can be suppressed due to reduction of overall compressive strain within the stacked QDs. We demonstrate ground-state lasing at 1.265 μm of six layers of InAs/GaAs QDs with GaP SC layers. The threshold current density is as low as 108 A/cm2. We also assess the internal loss and maximum modal gain of fabricated QD lasers by using a segmented contact method. The internal loss is as low as 5 cm-1, and the maximum modal gain of the ground state of the stacked QDs is approximately 10 cm-1.