Rinse garbanzo beans; transfer to a bowl. In a screw-top jar combine oil, vinegar, garlic, rosemary, salt, and pepper. Cover and shake well. Pour over beans; toss to coat. Cover and chill for at least 8 hours or up to 24 hours, stirring occasionally.
Let stand at room temperature about 30 minutes before serving. Drain beans or serve with slotted spoon.