Preheat the oven to 400 degrees F. Mix together the flour and oregano, and season with salt and pepper. Rinse and dry the chicken pieces, and then dredge them lightly in the seaoned flour mixture. In a heavy, ovenproof skillet, large enough to hold all of the chicken pieces, heat the olive oil, and then brown the chicken well on all sides over medium heat. Be careful not to burn the oil by using too hot of heat. Once all of the pieces are well browned, remove them to a plate. Pour out the left over oil in the pan, leaving just a tablespoon or two with the browned bits at the bottom. Add the onion and cook until soft, and then add the garic. As soon as the garlic begins to sizzle, add the wine, and stir the browned bits at the bottom while you reduce the wine by half over medium high heat. Add the chicken broth and bring to a boil. Break up the rosemary into pieces, and add it to the sauce. Return the chicken pieces to the skillet, and spoon the sauce over top. Bake the chicken until done, about 20 minutes.
Remove the chicken to a warmed platter, and bring the remaining sauce to a boil. Add the lemon juice and season with salt and pepper. Mix the tablespoon of flour with 1 tablespoon of softened butter. Add the remaining butter to the sauce in the skillet, and mix well. Remove the rosemary pieces from the sauce. If the sauce is thin, stir in a little of the flour and butter mixture, wisking continuously to prevent lumps. Once the sauce has thickened, add the chopped parsley, and pour the sauce over the chicken on the platter. Serve immediately.