Place 1 loaf of thawed dough in a well-oiled 9- by 13-inch baking pan. Press and stretch dough to fill pan evenly. (If dough is too elastic, let rest a few minutes and stretch again; repeat as necessary.)
Crumble feta in chunks evenly over dough. Sprinkle with half the rosemary and oregano, and pepper to taste.
On a lightly floured board, roll or stretch and pat second loaf into a rectangle roughly the shape of the pan. Lay over feta and herb-covered dough. Stretch top layer to completely cover bottom layer. Cover pan lightly with plastic wrap; let dough rise in a warm place until about doubled, 45 to 60 minutes.
Brush dough with oil. With your fingers, gently press dough down all over, forming dimples in the surface. Sprinkle with remaining rosemary and oregano.
Bake in a 400° oven until dough is well browned on edges and bottom (lift with a spatula to check), about 45 minutes. (If top starts to brown too much, lay a sheet of foil lightly on top during baking.) Loosen edges from pan sides and bottom. Turn focaccia out onto a rack, then invert again so bread is upright. Cool slightly.