Preheat the oven to 375°F (190°C) and lightly grease a muffin tin or line with silicone muffin liners.
Heat olive oil in a pan over medium heat. Add ¼ yellow onion and cook for 2–3 minutes.
Add 250 g mild Italian sausage and cook for about 4 minutes, breaking it apart occasionally until browned.
Add ½ red bell pepper and 1 cup spinach. Cook for another 4 minutes, until the sausage is cooked through.
Stir in ¼ cup kalamata olives olives, if using.
Using tongs or a spoon, divide the sausage and vegetable mixture evenly among the muffin cups.
In a large bowl, whisk together 8 eggs, ¼ cup dairy-free milk, ½ tsp garlic powder, ½ tsp Italian seasoning, ¼ - ½ tsp salt, and ¼ tsp black pepper.
Pour the egg mixture evenly into the muffin tin, filling each cup about ¾ full.
Bake for 18–22 minutes, or until the egg bites are set and reach an internal temperature of 165°F (74°C).
Let cool for 5 minutes before removing from the pan.
Enjoy!