This paper describes the effect of Sb pre-deposition on the composition modulation in InAsSb/InAs strained-layer multi-quantum wells. The multi-quantum-well structures, grown by metal-organic vapor-phase epitaxy (MOVPE) on InAs (1 1 1) substrates, had periods of approximate to 20 nm and nominal InAs0.8Sb0.2 layer thicknesses of approximate to 4.5 nm. Sb surface coverages from 0 to 1.4 monolayers (ML) were deposited on the InAs surfaces during growth interruptions prior to alloy layer growth. With no pre-deposition, kinematical simulations of measured theta-2 theta X-ray diffraction (XRD) patterns yielded best fits for exponential composition profiles as expected for Sb segregation. The lie Sb segregation lengths were 1.2-1.6 nm. When approximate to 0.8 ML of Sb was pre-deposited, XRD simulations indicated sharper InAsSb-on-InAs interfaces. Sb coverages of greater than or equal to 1 ML broadened the XRD superlattice reflections, indicating that interface roughness increased.