Thermoplastic elastomer compositions and methods for making same. The elastomer composition can include at least one partially cured rubber component that is an ethylene-alpha-olefin-vinyl norbornene elastomeric polymer, and at least one thermoplastic component. The rubber component is at least partially cured using a peroxide curative in an amount effective to yield a cure level of the rubber component of at least 85%. The rubber component has a molecular weight distribution (MWD) less than 6, and a branching index greater than 0.60.