The cforest function in the R partykit package has an argument applyfun, which the docs indicate can be used to apply “an optional lapply-style function with arguments function(X, FUN, …)“. I understand that mclapply does not function Windows OS, and parLapply is the ‘drop-in’ parallel alternative for lapply on Windows, which has the form parLapply(cl = NULL, X, fun, ...) as per the cforest documentation.