In this article we study the asymptotic behaviour of the realized quadratic variation of a process t 0 u s dG H s , where u is a β-Hölder continuous process with β > 1 − H and G H is a self-similar Gaussian process with parameters H ∈ (0, 3/4). We prove almost sure convergence uniformly in time, and a stable weak convergence for the realized quadratic variation. As an application, we construct strongly consistent estimator for the integrated volatility parameter in a model driven by G H .