This easy side dish is winter's answer to the Greek salad. Lightly cooking the tomatoes and garlic sweetens their flavors, while wilting the escarole mellows its bite.
In a large skillet, heat oil over medium-high. Add garlic, olives, and tomatoes; cook until tomatoes are soft, about 2 minutes; transfer to a plate. Add escarole to skillet and cook, stirring occasionally, until escarole is wilted, about 3 minutes. Season with salt and pepper, return olive mixture to skillet, and stir in vinegar to taste. Serve immediately.