The talk will follow an operadic approach to provide a bialgebraic description of substitution for Lie-Butcher series. I will first show how the well-known bialgebraic description for substitution in Butcher's B-series can be obtained from the pre-Lie operad. I will then apply the same construction to the post-Lie operad to arrive at a bialgebra Q. By considering a module over the post-Lie operad, we get a cointeraction between Q and the Hopf algebra H_MKW that describes composition for Lie-Butcher series. This coaction is then used to describe substitution for Lie-Butcher series.