Preheat broiler. Heat oil in large ovenproof skillet over medium-high heat. Add onions and broccoli and cook 5 minutes or until vegetables are crisp-tender. Reduce heat to medium.

Combine eggs, 1/2 cup of cheddar cheese, garlic powder, sea salt, and black pepper in a medium bowl and mix well. Pour egg mixture over vegetables in skillet. Cook, uncovered, gently lifting sides of frittata so uncooked egg flows underneath. Cook 7 to 8 minutes or until bottom frittata is golden brown and center is almost set.

Sprinkle with remaining 1/4 cup cheddar cheese and broil about 5 inches from heat for 3 to 5 minutes or until golden brown. Cut into wedges. Serve immediately.