Bring a large pot of lightly salted water to a boil. Add beet greens and cook, uncovered, until tender, about 2 minutes, and drain in a colander.
Immediately immerse in ice water for several minutes to stop the cooking process.
Once the greens are cold, drain well, and coarsely chop.
Heat olive oil in a large skillet over medium heat. Stir in garlic and red pepper flakes; cook and stir until fragrant, about 1 minute. Stir in the chopped greens until coated, then season with salt and pepper. Cook just until greens are hot; 1 to 2 minutes. Serve with lemon wedges.