Heat the oil in a large skillet over low-medium heat. Add the scallions, corn, salt and pepper, the cumin, and oregano. Stir to coat. Cover and cook for about 6 minutes, stirring frequently until the corn is tender. Add the beans, tomatoes, cilantro, and feta cheese. Stir to combine. Cover and cook for 2 minutes, stirring frequently, until just heated through. Taste for seasonings.
Remove the skillet from the heat. Line two cookie sheets with parchment paper or spray them with olive oil spray. Arrange 3 tortillas on each prepared cookie sheet. Spoon one-sixth of the filling onto each tortilla. Scatter the cubes of mozzarella evenly over the filling. Fold each tortilla over the filling and gently press to seal. Bake for about 12 minutes, until the tortillas are soft-crisp. Remove from the oven and serve with salsa and fat-free sour cream.