Preheat the oven to 300 degrees . In a large, heavy ovenproof pot or Dutch oven, cook the chicken in EVOO over high until browned, 5 minutes per side; transfer to a plate. Cook the pepper slices, stirring often, 2 minutes; transfer to another plate. Add the chopped pepper, garlic and 1 1/2 tsp. rosemary; cook, stirring, 1 minute. Stir in the next 4 ingredients; boil. Transfer to blender; puree and season.
In the pot, layer the potatoes, reserved chicken, pepper slices and sauce. Cover, and cook in oven until chicken is cooked through, about 50 minutes, Divide among plates; sprinkle with remaining rosemary.