A Turing mode in an extended periodically forced oscillatory system can change the classical resonance boundaries of a single forced oscillator. Using the normal form equation for forced oscillations, we identify a Hopf-Turing bifurcation point around which we perform a weak nonlinear analysis. We show that resonant standing waves can exist outside the 2:1 resonance region of uniform oscillations, and non-resonant mixed-mode oscillations may prevail inside the resonance region.