In small saucepan, bring 1/2 cup (125 mL) water to a boil. Stir in quinoa. Reduce heat to low and simmer, covered, for 15 minutes. Remove from heat and let stand for 5 minutes. Fluff with a fork. Set aside.
Preheat oven to 375°F (190°C).
Slice zucchini in half lengthwise. Scoop seeds onto work surface. Roughly chop seeds. Measure out 1/3 cup (75 mL) of chopped zucchini seeds; discard remainder.
In bowl, stir together measured zucchini seeds, cooled quinoa, tomatoes, green onions, feta, olive oil, garlic seasoning and egg white. Spoon mixture evenly into zucchini halves. Place in 8–inch square (2 L) glass baking dish. Add 1/2 cup (125 mL) water to bottom of dish. Bake uncovered) in centre of oven for 35 minutes or until zucchini is tender.