B^0_d-B-bar^0_d oscillations are observed in "self-tagged" samples
of partially reconstructed B mesons decaying into a lepton and a charmed meson
collected in ppbar collisions at sqrt s = 1.8 TeV.  A flavor tagging technique
is employed which relies upon the correlation between the flavor of B mesons
and the charge of nearby particles.  We measure the flavor oscillation
frequency to be Delta m_d = 0.471^+0.078_ -0.068 +/- 0.034 ps^-1.  The tagging
method is also demonstrated in exclusive samples of B^=_u -> J/psi K^+ and
B^0_d -> J/psi K^*0(892), where similar flavor-charge correlations are
observed.  The tagging characteristics of the various samples are compared
with each other, and with Monte Carlo simulations.