Optical burst switching (OBS) is a promising technology for optical grids with short-lived and interactive data communication requirements. On the other hand, burst losses are in the nature of the OBS protocol and these losses severely affect the grid job completion times. This paper first proposes a joint grid resource and network provisioning method to avoid congestion in the network in order to minimize grid job completion times. Simulations show that joint provisioning significantly reduces completion times in comparison to other methods that perform network provisioning after grid scheduling. An adaptive extra offset based quality of service (QoS) mechanism is also proposed in order to reduce grid burst losses in case of network congestion. Results show that this adaptive mechanism significantly reduces grid completion times by exploiting the trade-off between decreasing loss probability and increasing delay introduced by the extra offset time. (C) 2009 Elsevier B.V. All rights reserved.