In an oven-safe Dutch oven or large saucepan, fry the bacon until crisp. Remove with slotted spoon to paper towels to drain. Over medium heat, brown chicken pieces in the bacon drippings, turning to brown all sides.
Remove to a platter as chicken browns.
Add onions to the pan and cook until tender, about 4 to 5 minutes. Drain off excess fat. Sprinkle on the flour, marjoram, pepper, thyme, salt, sugar, and garlic. Stir in beer. Cook over medium-high heat, stirring constantly, until thickened and bubbly. Stir in vinegar. Add chicken back to pot. Sprinkle with bacon. If necessary, transfer to a large baking dish. Cover and bake at 350° for 55 to 65 minutes, or until chicken is tender.