Cook 3 sliced garlic cloves and 1/4 teaspoon red pepper flakes in 2 tablespoons olive oil over medium heat, 1 minute. Add 1 pound stemmed baby bell peppers. Cook, stirring, 5 minutes. Add 1/2 cup water and 2 tablespoons balsamic vinegar. Cover and cook 10 minutes. Season with salt; top with chopped oregano.