Combine first 3 ingredients in a small bowl, stirring until well-blended. Let stand 5 minutes.
Dissolve yeast and 1 1/2 teaspoons sugar in warm water in a large bowl; let stand 5 minutes. Lightly spoon flour into dry measuring cups; level with a knife. Add oat mixture, 1 3/4 cups flour, buttermilk, margarine, and salt to yeast mixture, stirring to form a soft dough. Turn dough out onto a lightly floured surface. Knead until smooth and elastic (about 8 minutes); add enough of remaining flour, 1 tablespoon at a time, to prevent dough from sticking to hands. (Dough will be slightly sticky).
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in bulk. Punch dough down; cover and let rest 5 minutes. Divide dough into 12 equal portions. Working with 1 portion at a time (cover remaining dough to keep from drying), shape each into a ball. Place balls in a 9-inch square baking pan coated with cooking spray. Cover and let rise 30 minutes or until doubled in bulk.
Preheat oven to 375°.
Uncover the dough. Combine 1 tablespoon water and egg white; brush over dough. Sprinkle dough with 1 tablespoon oats. Bake at 375° for 25 minutes or until lightly browned. Serve warm.