Heat oven to 400° F. In a food processor, pulse the bread and 2 tablespoons of the oil to form coarse crumbs.
Spread the crumbs on a baking sheet and bake until crisp, 5 to 6 minutes. Toss with the scallions, ½ teaspoon salt, and 1/8 teaspoon pepper.
Meanwhile, heat 1 tablespoon of the oil in a large ovenproof skillet over medium-high heat. Season the pork with ½ teaspoon each salt and pepper and brown, 2 to 3 minutes per side.
Transfer to oven and roast until cooked through, 5 to 7 minutes.
Toss the spinach, beans, vinegar, oregano, remaining tablespoon oil, ½ teaspoon salt, and 1/8 teaspoon pepper.
Top the pork with the bread-crumb mixture. Serve with the salad.