Preheat the oven to 450 degrees. Put the oil in a large oven safe skillet and heat on medium-high. When the oil shimmers but before it smokes, arrange the sprouts in one layer, cut side down. Add garlic and season with salt and pepper.
Cook, undisturbed, until the sprouts begin to brown, about 5 minutes. Move the pan to the over and cook, shaking the pan occasionally, until the sprouts are very brown and tender, about 30 minutes.
Drizzle with the vinegar and adjust seasoning as necessary. Stir and serve.