It is important to use plain lunch-size brown bags. If you use one with a logo, the ink will run.
Heat oven to 425 degrees. Combine garlic, lemons, bay leaves, rosemary, salt, and pepper in a large bowl. Remove tough outer leaves from artichokes; trim tops and stems. Cut artichokes in half, and scoop out and discard purple choke; add to bowl. Squeeze lemon juice over artichokes, and toss well.
Fill four brown bags with artichoke mixture, making sure to get an even mix of ingredients in each, especially artichokes and lemons. Cinch bags, and tie with string. Bake on a baking sheet until artichokes are tender and garlic cloves are very soft, about 1 hour. Spritz bags with water several times while baking. Tear open bags, and serve immediately with a drizzle of oil.