In this paper, we define the notion of generalized $\Gamma$-derivation for $\Gamma$-nearring and extend some results of $\Gamma$-derivation of $\Gamma$-nearrings for generalized $\Gamma$-derivation. Also a Posner type result for the composition of generalized $\Gamma$-derivations is obtained with some extra condition. Furthermore, examples are given to demonstrate that the restrictions imposed on the hypothesis of the various theorems were not superfluous.