Preheat the oven to 350°F. Line a 12‑cup muffin tin with silicone liners or spray each cup generously with nonstick spray.
In a medium bowl combine the chopped spinach, roasted red pepper, sliced green onion, shredded Monterey Jack and crumbled feta; mix gently so the cheeses coat the veggies evenly.
Pour the egg whites and cottage cheese into a tall container and use an immersion blender (or regular blender/food processor) to blend until mostly smooth, about 20–30 seconds. Season with smoked paprika, salt and pepper and pulse once more to incorporate.
Divide the vegetable and cheese mixture evenly among the 12 muffin cups — aim for the fillings to occupy the bottom third of each cup.
Carefully pour the egg and cottage cheese mixture over the fillings, filling each cup about three‑quarters full. Tap the pan once on the counter to release any large air bubbles.
Bake on the middle rack until the centers are set and tops are lightly golden, 22–25 minutes. A toothpick inserted in the center should come out clean or with just a few moist crumbs.
Remove the pan from the oven and let the bites rest in the tin for 6–8 minutes to finish setting. Use a small offset spatula or butter knife to loosen the edges, then transfer the bites to a cooling rack.
Serve warm, or cool completely and refrigerate in an airtight container. Reheat gently in the microwave for 20–30 seconds when ready to enjoy.