Grid Computing is a relatively new, distributed computing technology, based on sharing different types of computational resources, located in various geographic locations. Technical knowledge of grid users is expected to decrease in the future; that is why the usability of Grid Computing applications will become a main issue. Grid Computing applications are usually intercultural collaboration platforms. Moreover, Grid Computing applications' development is usually an intercultural challenge. A methodology for evaluating the usability of Grid Computing based applications has to be established. A set of heuristics is proposed, in order to help the heuristic evaluations of such applications.