The dynamics of resonant Rayleigh scattering (RRS) from excitons localized in a disorder potential with large monolayer islands is investigated theoretically and experimentally. Experimentally, the coherent RRS dynamics from GaAs single quantum wells (SQWs) is deduced by means of passively stabilized spectral interferometry. The new technique is discussed in detail. The results retrieved by spectral interferometry are complemented by data obtained by time-resolved and spectral speckle analysis. A strong dependence of the monolayer thickness of the SQW on the RRS spectra and the RRS dynamics is found. Changes in the well width corresponding to a fraction of one monolayer lead to drastic changes in the spectral and time-resolved RRS intensity. A comparison between spectra and dynamics contradicts the assumption of uncorrelated exciton levels. The RRS intensity is derived theoretically by solving the Schrodinger equation for the center-of-mass motion of the 1s-exciton in a disorder potential taking into account both interfaces with monolayer islands, the short range correlated disorder by segregation, and a correlation between the interfaces. The simulations reproduce qualitatively all observed features, determining in this way the characteristic disorder parameters like island sizes and interface roughness. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.