The influence of an equation of state on the dynamical (in)stability of a sphere undergoing dissipative collapse is investigated for various forms of matter distributions. Employing a perturbative scheme we study the collapse of an initially static star described by the interior Schwarzschild solution. As the star starts to collapse it dissipates energy in the form of a radial heat flux to the exterior spacetime described by the Vaidya solution. By imposing a linear equation of state of the form p_r = γ μ on the perturbed radial pressure and density we obtain the complete gravitational behaviour of the collapsing star. We analyse the stability of the collapsing star in both the Newtonian as well as the post-Newtonian approximations.