Dice the red onion and bell pepper into small, uniform pieces.
Slice the chicken sausage into thin rounds.
In a medium bowl, whisk together the large eggs, egg whites, sea salt, black pepper, and garlic powder until well combined.
Heat the olive oil in a non-stick skillet over medium heat.
Add the chicken sausage, onions, and bell peppers to the skillet, sautéing for 4 to 5 minutes until the vegetables are tender and the sausage is lightly browned.
Pour the egg mixture into the skillet, letting it sit for 30 seconds before gently folding with a spatula.
When the eggs are nearly set, add the baby spinach and continue to fold until the leaves are just wilted.
Transfer the scramble to a plate and top with fresh avocado slices.