Cut off the chard stalks near the base of the leaves and discard. Cut any large leaves in half lengthwise.
Heat the oil in a large skillet over medium heat. Add the pine nuts and garlic and cook, stirring, until golden, about 2 minutes. Stir in the chard, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Cook, stirring, until the chard ribs are just tender, 2 to 3 minutes.
Transfer to a serving bowl and sprinkle with the Feta.