Rheology-modified thermoplastic elastomer compositions comprising a melt blend of an ethylene/a-olefin polymer and a high melting polymer such as polypropylene or a propylene/a-olefin copolymer wherein the rheology modification is induced by a combination of a peroxide and a free radical coagent. The resulting compositions have an elastomeric phase, a non-elastomeric phase and certain physical properties that exceed those of a like composition that is rheology-modified by peroxide alone. The compositions can be used to make a variety of articles of manufacture, such as automotive instrument panel skins, via calendaring and thermoforming procedures.