Over medium-high heat, add 2 more tablespoons of vegetable oil. Add squash cubes. Stir briefly, then arrange in a single layer, and cook without stirring for about 5 minutes to brown the bottom sides. Sprinkle with cumin, salt and pepper, and stir to turn cubes
and continue to cook until tender and browned all over. Adjust salt and pepper to taste, then add scallion greens. Remove from heat, and add crumbled feta.