Heat olive oil in a large skillet over medium high heat. Add onion and garlic and cook for 5 minutes, or until the onion is tender.
Prepare the collard greens by removing the stems and slicing the leaves into 1-inch strips. Add the greens to the skillet and cook for 5 minutes, stirring occasionally.
Add the water and bring to a boil. Cover, and cook for 15 to 20 minutes, or until the greens are tender and the water is mostly evaporated. Remove from heat and stir in the red wine vinegar.
Serve with salt and pepper, lemon wedges (optional), and enjoy warm!