The challenge to develop innovative FF solutions for online orders has rapidly grown into a huge challenge for brick-and-mortar retailers. Pure online players have increasingly been able to challenge them on in-store sales, and the advantage of focusing purely on in-store sales is no longer sustainable. Retailers are in a perpetual quest for new methods of fulfilling online orders and arranging last-mile logistics. Lead-time reduction, in this case, has become an important requirement. Of the newest approaches for doing so, the OC approach via using already existing infrastructure, by incorporating DCs and local stores into one FF system is among others. Therefore, this paper introduces the fast integrated order FF concept in grocery retailing and meets new challenges arising from this development. Empirical analysis yields cos t items pertinent to decisions regarding order processing in a store, and a procedure for computing total FF costs is constructed. The policy involves allocating orders to different depots and determining routes at each of these depots as a function of their particular FF costs. An especially designed cluster-first, route-second heuristic is applied. The results indicate that the integrated rapid order FF saves approximately 7.4% of costs over a DC-based FF. However, because the in-store order processing will still be the key cost factor, this does not mean that DCs will be entirely substituted with store-based FF. All these results reflect the need for modeling the in-store processing costs much more precisely when deciding FF over a diverse network.