Bring a large pot of water to a boil and salt lightly. Trim the tough lower stems from the broccoli rabe and discard. Chop the tops and remaining stem into 2-inch pieces; you should have about 4 quarts of florets, leaves and stems. Drop the broccoli rabe into the boiling water and cook until tender, about 2 to 3 minutes, drain.
Heat the oil in a large sauté pan and add the broccoli rabe, garlic and ¼ teaspoon of salt and a pinch each of pepper and red pepper flakes. Cook for 2 or 3 minutes over medium heat, using metal tongs to toss the greens. Adjust the seasoning with salt and red pepper flakes.