  The star-forming efficiency of dense gas is thought to be set within cores by
outflow and radiative feedback. We use magneto-hydrodynamic simulations to
investigate the relation between protostellar outflow evolution, turbulence and
star formation efficiency. We model the collapse and evolution of isolated
dense cores for $\gtrsim$ 0.5 Myr including the effects of turbulence,
radiation transfer, and both radiation and outflow feedback from forming
protostars. We show that outflows drive and maintain turbulence in the core
environment even with strong initial fields. The star-formation efficiency
decreases with increasing field strength, and the final efficiencies are
$15-40$\%. The Stage 0 lifetime, during which the protostellar mass is less
than the dense envelope, increases proportionally with the initial magnetic
field strength and ranges from $\sim 0.1-0.4$ Myr. The average accretion rate
is well-represented by a tapered turbulent core model, which is a function of
the final protostellar mass and is independent of the magnetic field strength.
By tagging material launched in the outflow, we demonstrate that the outflow
entrains about $3$ times the actual launched gas mass, a ratio that remains
roughly constant in time regardless of the initial magnetic field strength.
However, turbulent driving increases for stronger fields since momentum is more
efficiently imparted to non-outflow material. The protostellar outflow momentum
is highest during the first 0.1 Myr and declines thereafter by a factor of
$\gtrsim 10$ as the accretion rate diminishes.
