In situ studies have been performed on thin films in the Al rich region of the Al-Cu-Fe-Cr quasicrystalline phase field. Thin films were grown by magnetron sputtering on atomically flat MgO (001) and Al2O3 (0001) and subsequently studied by transmission electron microscopy and X-ray photoelectron spectroscopy. High resolution electron microscopy shows that thin films ( < 30 nm) grown at room temperature are essentially amorphous. At higher temperatures ( > 573 K), the film growth is identified to be island mode. Upon subsequent ultra high vacuum annealing at 583 K, the films transform into a mixture of quasicrystalline and crystalline grains. Further annealing results in grain growth. A hexagonal crystalline phase in the films with a= 2.23 nm and c = 1.25 nm was identified as an approximant of the decagonal phase. For annealing temperatures above 848 K, the films phase separate into thick quasicrystalline and thin crystalline regions.