A composition having a) an ethylene-based copolymer made of units derived from ethylene and units derived from at least one comonomer of Structure I, wherein R is a C1-C2 hydrocarbyl group and R′ is a C1-C4 hydrocarbyl group; b) at least one antioxidant; c) from greater than 0 wt % to less than 3 wt % of an organic peroxide, based on the total weight of the composition; d) optionally, at least one co-agent; and e) optionally, at least one tree retardant, wherein the ethylene-based copolymer has a melt temperature (Tm) (° C.) and a comonomer content in moles per 100 grams ethylene-based copolymer (mol/100 g) (comonomer) that satisfies the relationship Tm