Preheat oven to 375°F (190°C). Grease a 12-cup muffin tin with olive oil or cooking spray.
Chop spinach, dice cherry tomatoes, and slice green onions.
Whisk eggs, cottage cheese, milk, garlic powder, salt, and pepper in a large bowl.
Stir in spinach, tomatoes, green onions, and 1/3 cup cheddar.
Divide mixture evenly among muffin cups, filling each about three-quarters full.
Sprinkle remaining 1/6 cup cheddar over the muffins.
Bake 22–25 minutes, until centers are set and tops are lightly golden.
Cool in the pan for 5 minutes, then remove and serve warm or store for meal prep.