We employ a new Infrared Flux Method (IRFM) temperature scale (Ramírez & Meléndez 2005a, b) in order to determine Li, O, and Fe NLTE abundances in a sample of relatively unevolved (dwarfs, turn-off, subgiants) metal-poor stars. We show that the analysis of the permitted OI triplet and FeII lines leads to a plateau in [OI/FeII] over the broad metallicity range $-3.2 <$ [Fe/H] $<-$0.7, independent of temperature and metallicity, and with a star-to-star scatter of only 0.1 dex. The Li abundance in halo stars is also found to be independent of temperature and metallicity (Spite plateau), with a star-to-star scatter of just 0.06 dex over the metallicity range $-3.4 <$ [Fe/H] $<-1$. Our Li abundance (Meléndez & Ramírez 2004) is higher than previously reported values, but still lower than the primordial abundance suggested by WMAP data and BBN.