Bring a large pot of salted water to a boil. Add the collard greens in batches and cook until just tender, about 10 minutes. Drain the greens in a colander and rinse under cold water to cool; squeeze to remove any excess water.
Heat the oil in a large saucepan over medium heat. Add the garlic and cook, stirring, for 1 minute. Add the greens, 1 teaspoon salt, and ½ teaspoon pepper. Cook, tossing often, until wilted and tender, 3 to 4 minutes.