  We present an 870 $\mu$m continuum survey of 300 protostars from the Herschel
Orion Protostar Survey using the Atacama Compact Array (ACA). These data
measure protostellar flux densities on envelope scales $\leq$8000 au (20") and
resolve the structure of envelopes with 1600 au (4") resolution, a factor of
3-5 improvement in angular resolution over existing single-dish 870 $\mu$m
observations. We compare the ACA observations to Atacama Large
Millimeter/submillimeter Array 12 m array observations at 870 $\mu$m with
$\sim$0.1 (40 au) resolution. Using the 12 m data to measure the fluxes from
disks and the ACA data within 2500 au to measure the combined disk plus
envelope fluxes, we calculate the 12 m/ACA 870 $\mu$m flux ratios. Our sample
shows a clear evolution in this ratio. Class 0 protostars are mostly
envelope-dominated with ratios $<$0.5. In contrast, Flat Spectrum protostars
are primarily disk-dominated with ratios near 1, although with a number of
face-on protostars dominated by their envelopes. Class I protostars span the
range from envelope to disk-dominated. The increase in ratio is accompanied by
a decrease in the envelope fluxes and estimated mass infall rates. We estimate
that 80$\%$ of the mass is accreted during the envelope-dominated phase. We
find that the 12 m/ACA flux ratio is an evolutionary indicator that largely
avoids the inclination and foreground extinction dependence of spectral energy
distribution-based indicators.
