Preheat oven to 400F, grease a 9 x 13 casserole dish. Line a sheet pan with foil and grease the foil.
Chop potatoes, then toss with 1/2 teaspoon garlic, 1/8 teaspoon salt, 1/8 teaspoon pepper.
Add potatoes to half of the sheet pan and roast in the oven for 10 minutes. When the 10 minutes is up, add the broccoli, spray with cooking spray and sprinkle with salt. Roast for an additional 10 minutes, remove from oven and turn it down to 375F.
While potatoes and broccoli are cooking, cook the breakfast sausage. Add chopped onion to large nonstick skillet with 1 tbsp avocado oil, saute until translucent, about 1-2 minutes. Add ground breakfast sausage and cook it all the way through.
When the potatoes and broccoli are done, spread them evenly on the bottom of the casserole. Next add peppers, tomatoes, and spinach. Then add the breakfast chicken sausage.
Whisk 12 eggs together with 1 tsp garlic powder, 1 tsp onion powder, 1/4tsp salt, and 1/8 tsp black pepper. Pour whisked eggs over the casserole.
Gently move veggies in egg mixture to make sure everything is fully coated. Bake for 45-55 minutes, or until eggs are set. Let cool 10 minutes before serving!