01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease lightly.
02 - Whisk together flour, baking powder, baking soda, salt, and black pepper in a large bowl.
03 - Beat eggs, whole milk, and olive oil or melted butter in a separate bowl until fully combined.
04 - Pour wet mixture into dry ingredients and gently stir until just combined, avoiding overmixing.
05 - Carefully fold in cheddar, feta, bell pepper, spinach, chives, and parsley until evenly distributed.
06 - Divide batter evenly among muffin cups, filling each about three-quarters full.
07 - Bake for 22 to 25 minutes, or until golden brown and a toothpick inserted into the center comes out clean.
08 - Allow muffins to cool in tin for 5 minutes, then transfer to a wire rack. Serve warm or at room temperature.