Dissolve sugar and yeast in warm water in a large bowl, and let stand 5 minutes. Lightly spoon the flours into dry measuring cups, and level with a knife. Stir all-purpose flour, 2 cups whole-wheat flour, vegetable oil, and salt into yeast mixture. Turn dough out onto a lightly floured surface. Knead until dough is smooth and elastic (about 8 minutes), and add enough of the remaining whole-wheat flour, 1 tablespoon at a time, to prevent dough from sticking.
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 dough and let rest 20 minutes. Divide dough in half. Working with one portion at a time (cover remaining dough to keep from drying), roll each portion into a 6 x 4-inch rectangle on a lightly floured surface. Roll up each rectangle tightly, starting with a long edge, pressing firmly to eliminate air pockets; pinch seam and ends to seal. Place rolls, seam sides down, in 2 (8 x 4-inch) loaf pans coated with cooking spray. Cover and let rise 30 minutes or until doubled in bulk.
Preheat oven to 350°.
Uncover dough. Combine sunflower seed kernels, oats, and margarine; brush over loaves. Bake at 350° for 30 minutes or until loaves sound hollow when tapped. Remove from pans; cool on wire racks.