Specular ion current measurements, where an ion beam impinges at a glancing angle to the surface and the specularly reflected beam is measured, were used to monitor GaAs molecular beam epitaxy on GaAs(001) surfaces. Scattered ion current oscillations were observed during growth with periods corresponding to monolayer growth times. Kinetic rate equation modeling of growth showed periodic variations in the density of two-dimensional islands; the oscillations arose due to nonspecular ion scattering from step edges. The ion current recovered after growth, and the data were fit well by assuming simple power-law coarsening of two-dimensional islands. The fits provided information on coarsening processes, and the average island size and density at the end of growth. Island statistics vs growth time were obtained by fitting recoveries for growths stopped at various stages. Islands were initially detected at 0.1-0.2 ML, with an initial size of 46 nm(2) and density of 4 x 10(11) cm(-2) . The island size remained relatively constant while the density increased rapidly as the coverage increased to approximate to 0.4 ML. As the coverage increased above this value, the island density leveled off and then decreased as the size increased, indicating island coalescence.