Compatibilism is the idea that Free Will is compatible with Determinism. Compatibilists believe that as long as our Mind is one cause in the causal chain that we can be responsible for our actions, which is reasonable. But they think every cause, including our decisions, are pre-determined. Compatibilists are Determinists.
The important question for Compatibilists is "Which Determinism is is that you think is compatible with Free Will?"
The argument that Free Will is compatible with God's foreknowledge is quite different from the argument for compatibility with Biological Determinism.
Please see our table of compatibilisms for each philosopher.