  The paper follows an operadic approach to provide a bialgebraic description
of substitution for Lie-Butcher series. We first show how the well-known
bialgebraic description for substitution in Butcher's $B$-series can be
obtained from the pre-Lie operad. We then apply the same construction to the
post-Lie operad to arrive at a bialgebra $\mathcal{Q}$. By considering a module
over the post-Lie operad, we get a cointeraction between $\mathcal{Q}$ and the
Hopf algebra $\mathcal{H}_N$ that describes composition for Lie-Butcher series.
We use this coaction to describe substitution for Lie-Butcher series.
