Preheat oven to 350°F (175°C). Lightly grease a muffin tin or line with silicone cups.
Add eggs, cottage cheese, olive oil, salt, and pepper to a blender. Blend until smooth.
Stir in bell pepper, spinach, green onions, and cheese (if using).
Pour mixture evenly into muffin cups, filling about 3/4 full.
Bake for 18–22 minutes, until centers are set and tops are just lightly golden.
Let cool for 5 minutes before removing from pan.