Preheat oven to 350 degrees and prep a muffin tin by spraying with oil (if using a silicone pan, no need for oil). Optional: fill a small dish of water and place in the oven to create a humid environment for egg bites and mimic the sous vide texture.
In a small sauté pan, sauté red bell pepper, spinach, and green onion in 1 tbsp of oil for 3-4 minutes. Transfer to a small bowl and cool in the fridge.
Add egg whites, cottage cheese, monterey jack cheese, feta cheese, hot sauce, salt and pepper to a large bowl (or a standard blender if you don't have an immersion blender).
Using an immersion blender, blend for 30 seconds until fully combined. If using a regular blender, blend on high for up to 30 seconds until combined.
Mix in cooled veggies.
Fill a muffin pan evenly and bake for 20-22 minutes until egg bites are fully cooked through and no longer "jiggly".
Notes
Be careful not to overfill the muffin tins. I recommend sticking to filling 1/2-2/3 of the way. If they're overfilled they tend to puff up out of the muffin pan and cook unevenly.