Halve the kielbasa lengthwise and slice into 1/2-inch pieces. Heat 1/2 tablespoon of oil in a large skillet over medium heat. Add the sausage and cook until browned, about 3 minutes per side. Transfer to a plate.

Reduce heat to medium-low. Add the remaining tablespoon of oil and the chopped onion. Cook until softened, about 5 minutes. Add garlic and cook for 1 minute. Add cabbage, salt, and pepper. Toss well, cover, and cook until cabbage is wilted, about 12 minutes, stirring every 4-5 minutes.

Stir in red wine vinegar and return sausage to the pan. Mix well, cover, and cook for 3 more minutes until the cabbage is tender and the sausage is hot. Taste and adjust salt if needed. Serve hot.