In this paper, we investigated the structural, electronic and optical properties of InAs, InN and InP binary compounds and their related ternary and quaternary alloys by using the full potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The total energies, the lattice parameters, and the bulk modulus and its first pressure derivative were calculated using different exchange correlation approximations. The local density approach (LDA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) approximations were used to calculate the band structure. Nonlinear variations of the lattice parameters, the bulk modulus and the band gap with compositions x and y are found. Furthermore, the optical properties and the dielectric function, refractive index and loss energy were computed. Our results are in good agreement with the validated experimental and theoretical data found in the literature.