The optoelectronic and thermoelectric properties of RbXO2 (X = Al, Ga, In) oxides have been investigated by using the density functional theory (DFT). The stability of RbXO2 has been confirmed from the negative value of enthalpy of formation, Goldschmidt's tolerance factor (0.91, 0.95 and 1.02) and Born mechanical stability criteria. The bandgap of the studied RbXO2 lies in the range from 3.3 eV to 1.25 eV, which shifts the optical region from near ultraviolet to near infrared region of spectrum. The comparative analysis of optical and thermoelectric properties shows RbXO2 are more suitable for optoelectronic applications than thermoelectric applications.