Arrange the sliced tomatoes in a large shallow dish. Combine the olive oil, red wine vinegar, salt, pepper, minced garlic, chopped onion and herbs in a jar. Cover tightly, and shake well. Pour the marinade over tomato slices.
Cover and refrigerate for several hours. Editor's Tip: If you made more marinade than you needed, just put the lid on the jar, and save it for a salad.