Let $(\Sigma_\bullet)$ be the collection of the symmetric groups. These have a structure of an operad in $\mathsf{Set}$ (it is in fact the operad $Ass$ encoding monoids). The collection of the classifying spaces $(\mathsf B \Sigma_\bullet)$ have thus an operad structure in $\mathsf{Top}$, the classifying space functor being strictly monoidal.
If $X$ is a space, the $n$-sheeted coverings of $X$ are classified by $\mathsf B \Sigma_n$. This means that isomorphism classes of (marked) coverings are in bijection with homotopy classes of (based) maps $[X, \mathsf{B} \Sigma_n]$.
The operad structure on the classifying spaces gives then naturally an operad structure on the family of sets $[X, \mathsf B \Sigma_\bullet]$. Therefore, the family of isomorphism classes of coverings of $X$ has a natural operad structure inherited from $Ass$.
(Equivalently, this could be recovered by saying that a covering is classified by a conjugacy class of a morphism $\pi_1(X,x_0) \to \Sigma_n$.)
I imagine there is a similar operad structure for vector bundles, replacing the symmetric groups with the general linear group. The operad structure on the classifying spaces (that is, the grassmannians) being induced by the direct sum. My question is : Is this structure interesting ? Has it been used somewhere ?