Projects that are resource intensive or interdisciplinary in scope, may require resources across many hardware platforms and may span NSF centers in their support requirements. Responding to these support requirements, the four NSF supercomputing centers formed the Grand Challenge Allocations Committee (GCAC). Drawing dynamically on the skills and talents of the combined local center peer review boards, the GCAC meets once a year to review proposals of this scope. The process streamlines proposal submission and administration of grants for the researcher, allowing them to request in one package whatever mix of platform and resource levels is appropriate to support their research.