We report the simple one-pot synthesis of size tunable zinc oxide nanoparticles (ZnO NPs) out of an organometallic ZnO precursor using the self-assembly of solution phase polystyrene-block-poly(2-vinylpyridine) micelles. The resulting hybrid material could be deposited on various substrates in a straightforward manner with the NPs showing size-dependent absorption and photoluminescence due to the quantum-size effect. We compare the results to the assembly of preformed NPs which are selectively incorporated in the poly(2-vinylpyridine) core of the micelles due to the high affinity of ZnO to vinylpyridine.