Heat oven to 250 degrees F. Bring large pot of water to a boil. Core tomatoes. With small knife, make small criss-cross cut through skin on end opposite cored end on each tomato.
Place each tomato in boiling water 30 seconds. Remove with slotted spoon and place immediately in bowl of ice water.
Peel skins from tomatoes. Cut tomatoes crosswise in half. Scoop out seeds.
Brush bottom and sides of 13 x 9 x 2-inch glass baking dish with some of the olive oil. Sprinkle half of the salt, pepper, garlic and thyme leaves over bottom of dish. Arrange tomatoes, cut side up, in dish. Sprinkle remaining olive oil, salt, pepper, garlic, thyme and the vinegar over top of tomatoes.
Bake in 250 degree F oven 2-1/2 to 3 hours, until soft and just beginning to caramelize or darken, but still holding their shape. Spoon juices from bottom over tomatoes. Serve from dish. Makes 6 servings.