In 1973, Ahlfors established a sufficient condition for an analytic function to be univalent in the unit disk |z|<1 and has a quasiconformal extension. Using his result, many known conditions for univalence and quasiconformal extendibility of analytic functions in the unit disk were deduced. Interestingly, his result was generalized to the class of harmonic mappings. The main aim of this paper is to present another generalization of Ahlfors's result by establishing p-valent conditions for biharmonic mappings defined in the unit disk and exterior. Moreover, we also determine conditions for a harmonic mapping of the unit disk to be univalent and has a quasiconformal extension.