The use of strained ternary and quaternary (In, Ga, Al) quantum wells for the active regions in MBE grown 1.5-mu-m lasers has been compared. Threshold current densities as low as 530 A/cm2 were obtained using compressively strained (In, Ga, Al)As quaternary quantum wells with waveguide losses of 9.4 cm-1 and a current injection efficiency of 83%. These results represent the best (Al, Ga, In)As/InP quantum well lasers grown by MBE.