  We present Spitzer IRS spectra and MIPS photometry of 12 radio-loud QSOs with
FR II morphologies at z ~ 0.3. Six of the sources are surrounded by luminous
extended emission-line regions (EELRs), while the other six do not have such
extended nebulae. The two subsamples are indistinguishable in their
mid-infrared spectra and overall infrared spectral energy distributions (SEDs).
For both subsamples, the mid-infrared aromatic features are undetected in
either individual sources or their stacked spectra, and the SEDs are consistent
with pure quasar emission without significant star formation. The upper limits
to the star formation rate are sufficiently low that starburst-driven
superwinds can be ruled out as a mechanism for producing the EELRs, which are
instead likely the result of the ejection of most of the gas from the system by
blast waves accompanying the launching of the radio jets. The FR II quasars
deviate systematically from the correlation between host galaxy star formation
rate and black hole accretion rate apparently followed by radio-quiet QSOs,
implying little or no bulge growth coeval with the current intensive black hole
growth. We also present a new Spitzer estimate of the star formation rate for
the starburst in the host galaxy of the compact steep-spectrum radio quasar 3C
48.
