Heat the olive oil over medium-high heat in a large pot or Dutch oven. Add the onions, and saute until just beginning to brown, about 5 minutes. Add the collards, and then the ham hock, garlic, chicken broth and some salt and pepper.
Bring to a simmer and cook until the greens are tender, about 45 minutes. Before serving, stir to break up the ham hock, and season with salt and pepper if needed.