The peak of the luminescence spectrum of zinc oxide (ZnO) is usually observed above 500 nm (yellow region). By in-situ growth of ZnO of ZnO nanoparticles in a poly(ethlyene glyco) (PEC) matrix, we have succeeded in producting ZnO polymer composites with stable luminescence peaks down to 463 nm (blue region). The unbalanced precursor molarity approach, where the molarity of one precursor (LiOH) of several times larger than the molarity represented by a chemical reaction balance, was used. The blue luminescence, which was accompanied by an enhancement of luminescence intensity, was observed at very high LiOH concentrations. This was probably due to the simultaneous reduction in the crystalline size and improvement in the crystallinity. Doping ZnO nanoparticle with europium also generated a red luminescence at 616 nm, due to the D-5(0)-->F-7(2) transition of Eu ions.