  We report two complementary measurements of the WW+WZ cross section in the
final state consisting of an electron or muon, missing transverse energy, and
jets, performed using p\bar{p} collision data at sqrt{s} = 1.96 TeV collected
by the CDF II detector. The first method uses the dijet invariant mass
distribution while the second more sensitive method uses matrix-element
calculations. The result from the second method has a signal significance of
5.4 sigma and is the first observation of WW+WZ production using this
signature. Combining the results gives sigma_{WW+WZ} = 16.0 +/- 3.3 pb, in
agreement with the standard model prediction.
