During the execution of a process, managing the collaboration inside a task performed by various actors is not straightforward due to possible changes of the process's context and the collaboration strategy. Process management solutions which describe the collaboration at modeling time offer a rigid control for conducting such collaborative tasks and thus cannot adapt to changes. To enable a flexible execution of collaborative tasks, we propose using the late-binding mechanism to allow process actors, at execution time, choosing or adapting strategies to perform their collaboration. To do so, first we model collaboration strategies as process patterns providing different ways to implement a collaborative tasks at execution time. These collaboration patterns describe how to establish necessary relations for coordinating different instances of the task, for sharing and exchanging working artifacts among actors performing those instances. Then we define actions to execute collaborative tasks. These actions take collaboration patterns as parameters. Thus, by letting process actor selecting a suitable collaboration pattern, they allow binding dynamically a collaborative task to its implementation flexibly.