We report our recent development of a fabrication method for monolithic semiconductor waveguided optoelectronic integrated circuits (OEICs) using selective area epitaxy. Selective-area growth (SAG) may can produce an energy band gap variation in the waveguide structure within the same wafer. Therefore, devices such as amplifiers, modulators, and splitters that require different energy band gaps for the same operating wavelength may be fabricated monolithically to avoid the high cost and the signal degradation associated with the hybrid integration. However, epitaxial regrowth is still used in most SAG device fabrication. To further lower the cost and simplify the OEICs fabrication, we proposed a one growth and one waveguide fabrication method. This method requires a single metal-organic-chemical-vapor-deposition (MOCVD) growth of the whole InGaAsP multiple quantum well-waveguide core and InP bottom and top cladding layers on an InP substrate masked by parallel SiO2 strips. A localized shift of the band gap, that is induced by variations in epilayer thickness and composition, can be controlled by varying the width of the SiO2 strips and the gap between the strips. We have developed a special waveguide device processing technique for this type of non-uniform SAG materials. The challenge is to obtain the right energy bandgaps, right quantum well widths, right p-i-n electric fields in different waveguide device sections, and maintaining appropriate optical mode profile when the waveguides pass through the layer thickness and composition variations as well as bending curvatures. For the devices discussed here, extensive optical, electrical, and SEM characterizations have been performed to optimize the structure design and processing parameters. A few combinations of integrated waveguide splitters, modulators, and amplifiers have been designed and fabricated. Preliminary device testing has been performed.