Heat 1 tbsp. oil in large ovenproof skillet over medium-high heat. Add red pepper and cook, stirring often, until it begins to soften, about 1 min. Add mushrooms and cook, stirring often, until juices evaporate, about 5 min. Stir in scallions and cook until wilted, about 1 min. Transfer to plate.

Season pork with 1/2 tsp. salt and 1/4 tsp. pepper. Add remaining 1tbsp. oil to skillet and heat. Add pork and cook, turning occasionally, until browned and meat is slightly pink when pierced to the center with tip of sharp knife, about 5 min. Sprinkle with flour and stir with wooden spoon to coat pork.

Add wine and 1/2 c. water and bring to a boil, scraping up browned bits in pan with wooden spoon. Return vegetables to pan and cook until sauce is thickened, about 1 min. Season with salt and pepper. Serve hot.