A range of reactor grade TPO alloys (PP/EPM alloys from Ziegler-Natta catalysis) were studied in order to evaluate their dynamic cross-linkability, using a peroxide system. The amount of ethylene content in EPM rubber ranged from 28 to 77 wt%, to investigate the competition between vis-breaking and cross-linking during the peroxide reaction. Processing temperature and different peroxide/coagent ratios were the parameters varied in the present work. Cross-linking degree was evaluated with Compression Set measurements and Dynamic Mechanical Analysis. It was therefore possible to find a correlation between the two analytical techniques. Feasibility of TPV rubbers with Compression Set at about 50% (22 h, 70degreesC) was demonstrated.