  Quasilocal definitions of stress-energy-momentum---that is, in the form of
boundary densities (in lieu of local volume densities)---have proven generally
very useful in formulating and applying conservation laws in general
relativity. In this essay, we take a first basic look into applying these to
cosmology, specifically using the Brown-York quasilocal stress-energy-momentum
tensor for matter and gravity combined. We compute this tensor and present some
simple results for a flat FLRW spacetime with a perfect fluid matter source.
