  We look at joint regular variation properties of MA($\infty$) processes of
the form $\mathbf{X} = (X_k, k \in \mathbb{Z})$ where $X_k =
\sum_{j=0}^{\infty} \psi_j Z_{k-j}$ and the sequence of random variables $(Z_i,
i \in \mathbb{Z})$ are i.i.d. with regularly varying tails. We use the setup of
$\mathbb{M}_{\mathbb{O}}$-convergence and obtain hidden regular variation
properties for $\mathbf{X}$ under suitable summability conditions on the
constant coefficients $(\psi_j : j \geq 0)$. Our approach emphasizes continuity
properties of mappings and produces regular variation in sequence space.
