  We characterize the optical variability properties of eight lobe-dominated
radio quasars (QSOs): B2 0709$+$37, FBQS J095206.3$+$235245, PG 1004$+$130,
[HB89] 1156$+$631, [HB89] 1425$+$267, [HB89] 1503$+$691, [HB89] 1721$+$343, 4C
$+$74.26, systematically monitored for a duration of 13 years since 2009. The
quasars are radio-loud objects with extended radio lobes that indicate their
orientation close to the sky plane. Five of the eight QSOs are classified as
giant radio quasars. All quasars showed variability during our monitoring, with
magnitude variations between 0.3 and 1 mag for the least variable and the most
variable QSO, respectively. We performed both structure function (SF) analysis
and power spectrum density (PSD) analysis for the variability characterization
and search for characteristic timescales and periodicities. As a result of our
analysis, we obtained relatively steep SF slopes ($\alpha$ ranging from 0.49 to
0.75) that are consistent with the derived PSD slopes ($\sim$2--3). All the
PSDs show a good fit to single power law forms, indicating a red-noise
character of variability between $\sim$13 years and weeks timescales. We did
not measure reliable characteristic timescales of variability from the SF
analysis which indicates that the duration of the gathered data is too short to
reveal them. The absence of bends in the PSDs (change of slope from $\geq$1 to
$\sim$0) on longer timescales indicates that optical variations are most likely
caused by thermal instabilities in the accretion disk.
