Prepare a medium-sized pot of boiling salted water. Blanche greens until tender, about 3 minutes for kale and 2 minutes for Swiss chard. Drain, cool and squeeze dry. (Alternatively, cook in a large skillet over medium heat with 1 Tbsp. oil until tender. Remove from pan.)
Heat the oil in a large skillet over medium-high heat. Add leek and bell pepper or tomato. Cook, stirring occasionally, for 5 minutes or until tender.
Stir in quinoa and garlic. Cook uncovered for 3 - 4 minutes, or until grains start to turn opaque. The quinoa will not be completely cooked at this point.
Add 1 1/2 c. vegetable stock, a pinch of salt and black pepper, seasoning herb blend and red pepper flakes. Cover and reduce heat to medium-low and simmer for 15-20 minutes, until most liquid has been absorbed. Cooking time will depend on the quinoa.
Remove from heat and let stand for 5 minutes.
Preheat oven to 350°F/180°C. Coat an 8x8-in. baking dish with cooking spray.
Whisk together eggs and milk in a large bowl. Fold in quinoa mixture and 1 1/2 c. cheese. Stir to combine and let some of the cheese melt. At this point the mixture should be a little soupy. Add a bit more liquid if necessary.
Transfer to prepared baking dish and top within remaining 1/2 c. cheese and bread crumbs. Bake 25 - 35 minutes until browned around the edges.
Remove from oven, cut and serve. Top with scallions as garnish.