  The two-orbital Hubbard model on a square lattice at quarter filling
(electron number per site $n=1$) is investigated by the variational Monte Carlo
method. For the variational wave function, we include short-range doublon-holon
binding factors. We find that the energy of this wave function is lower than
that of the density-density Jastrow wave function partially including
long-range correlations used in a previous study. We introduce frustration to
the model by the next-nearest-neighbor hopping $t'$ in addition to the
nearest-neighbor hopping $t$. For $t'=0$, a ferromagnetic state with staggered
orbital order occurs by increasing the Coulomb interaction $U$ before the Mott
transition takes place. By increasing $t'$, the region of this ferromagnetic
phase shrinks, and the Mott transition without magnetic order occurs.
