  This paper presents XMM-Newton and Chandra X-ray spectroscopy of ten
flat-spectrum radio quasars (FSRQ) which are candidates to have an X-ray
spectrum dominated by jet synchrotron emission. In all these FSRQ, which are
less strongly relativistically beamed than blazars, a considerable contribution
from a power-law component similar to that present in radio-quiet quasars is
required to explain the observed X-ray fluxes and X-ray spectral slopes. And as
in radio-quiet quasars, their relatively high optical/UV fluxes can be
accounted for by a significant contribution from thermal accretion disk
emission. The lack of success in finding radio quasars with synchrotron X-rays
is attributed to the adopted selection criteria, which were based on the
multiwavelength flux ratios of BL Lacertae (BL Lac) objects. A refined
selection technique, which additionally involves radio imaging, is proposed to
search for these important candidates for the Gamma Ray Large Area Space
Telescope (GLAST). On the other hand, the discovered FSRQ with their strong
accretion disk signatures are expected to be important probes for studies of
the poorly known accretion disk - jet connection.
