  We systematically analyze the 6-year {\it Fermi}/LAT data of the
lobe-dominated quasars (LDQs) in the complete LDQ sample from 3CRR survey and
report the discovery of high-energy $\gamma$-ray emission from 3C 275.1. The
$\gamma$-ray emission of 3C 207 is confirmed and significant variability of the
lightcurve is identified. We do not find statistically significant $\gamma$-ray
emission from other LDQs. 3C 275.1 is the known $\gamma$-ray quasar with the
lowest core dominance parameter (i.e., $R=0.11$). We also show that both the
northern radio hotspot and parsec jet models can reasonably reproduce the
$\gamma$-ray data. The parsec jet model, however, is favored by the potential
$\gamma$-ray variability at the timescale of months. We suggest that some
dimmer $\gamma$-ray LDQs will be detected in the future and LDQs could
contribute non-negligibly to the extragalactic $\gamma$-ray background.
