Preheat the oven to 375°F (190°C). Lightly grease a 12-cup muffin tin or use silicone muffin liners.
Whisk the eggs in a large bowl. Add cheese, salt, black pepper, paprika, and garlic powder. Mix well.
Stir in the diced bell peppers, spinach, crumbled bacon, and green onions until evenly combined.
Divide the mixture evenly into the prepared muffin tin, filling each cup about 3/4 full.
Bake for 18–20 minutes or until the egg muffins are set and slightly golden on top.
Let them cool for a few minutes before carefully removing them from the tin.
Serve immediately, or store in the refrigerator for up to 5 days. You can also freeze them for up to 3 months.