Preheat oven to 400°F (200°C). Toss chopped broccoli with a little olive oil, salt, and pepper. Roast on a sheet pan for ~15 minutes, until tender and lightly browned.
Cook onions & sausage
In a skillet, sauté onion until soft. Add chicken sausage and cook until warmed through.
Whisk eggs
In a large bowl, whisk eggs with garlic powder, salt, and pepper. Stir in roasted broccoli, onions, sausage, and cheese.
Bake
Pour mixture into a greased 9x13-inch baking dish. Bake at 375°F (190°C) for 25–30 minutes, until center is set.
Cut rounds
Let cool slightly, then use a circular cookie cutter to make egg rounds.
Serve
Slide into bagels for a breakfast sandwich or refrigerate/freeze for meal prep.