Heat 1 teaspoon oil in a medium skillet over medium heat. Add red pepper, oregano, salt, spinach, and garlic; cook 3 minutes. Place spinach mixture in a medium bowl. Stir in 1 tablespoon Marsala, cheese, raisins, and capers; set aside.
Cut a horizontal slit through the thickest portion of each breast half to form a pocket. Stuff about 1/3 cup spinach mixture into each pocket. Secure each chicken breast with wooden picks. Dredge chicken breasts in breadcrumbs, turning to coat; shake off excess breadcrumbs.
Heat 2 teaspoons oil in pan over medium heat. Add chicken; cook 12 minutes or until chicken is browned, turning after 6 minutes. Remove from pan; keep warm. Add remaining Marsala and vinegar to pan. Combine water and cornstarch in a small bowl. Add cornstarch mixture to pan; bring to a boil. Cook 1 minute, stirring constantly; add chicken to pan. Cover, reduce heat, and simmer 6 minutes or until chicken is done. Drizzle remaining sauce over chicken.