We have imaged 45 quasars from the Sloan Digital Sky Survey ( SDSS ) with redshifts 1.85 < z < 4.26 in JHK _ { s } with the KPNO SQIID imager .
By combining these data with optical magnitudes from the SDSS we have computed the restframe optical spectral indices of this sample and investigate their relation to quasar redshift .
We find a mean spectral index of \langle \alpha _ { o } \rangle = -0.55 \pm 0.42 with a large spread in values .
We also find possible evolution of the form \alpha _ { o } = ( 0.148 \pm 0.068 ) z - ( 0.964 \pm 0.200 ) in the luminosity range -28.0 < M _ { i } < -26.5 .
Such evolution suggests changes in the accretion process in quasars with time and is shown to have an effect on computed quasar luminosity functions .