In a large ovenproof skillet, heat the oil until shimmering. Add the chicken skin side down and cook over moderately high heat, turning once, until browned all over, 7 minutes. Transfer the chicken to a platter skin side up.
Pour off all but 2 tablespoons of fat from the saute pan. Add the onion, garlic, crushed red pepper and bay leaf and cook over moderate heat, stirring, until the onion is softened.
Add the bell pepper and poblano and cook until softened. Stir in the tomato paste and cook for 1 minute.
Add the grape juice and boil for 2 minutes, scraping up any browned bits from the bottom of the skillet.
Add the tomatoes and their juices, the vinegar and marjoram sprigs and bring to a simmer. Add the chicken legs back to the pan, skin side up.
Bake in the upper third of the oven for 35 minutes, until the chicken is cooked through.
Discard the marjoram and season the sauce with salt and pepper.