Preheat oven to 350°F (175°C).
Sauté onions in olive oil over medium-high heat for 2-3 minutes.
Add peppers and continue cooking for another 2-3 minutes.
While peppers are cooking, whisk eggs in a large bowl.
Once onions/peppers are cooked, remove from heat and let cool for a few minutes. Dump in egg mixture and stir well, sprinkling in the salt and pepper.
Coat a large muffin pan with olive oil spray or coconut oil.
Using a ¼-cup (60 mL) measuring cup, fill each muffin cup.
Place in oven for 10–15 minutes.
Remove them once the tops get high, fluffy and golden brown. Pop them out with a butter knife or thin spatula.