Preheat and prep pans: Heat oven to 400°F (200°C).
Line a baking sheet or 9x13-inch dish with parchment for easy cleanup.
Prep the peppers: Slice each pepper in half lengthwise and remove seeds and membranes. Brush the cut sides with olive oil and sprinkle with a little salt and pepper.
Soften the peppers (optional but recommended): Place pepper halves cut side up on the sheet and pre-bake for 8–10 minutes. This helps them turn tender without getting watery.
Make the ranch filling: In a large bowl, mix cream cheese, sour cream, mayonnaise, ranch seasoning, garlic powder, onion powder, smoked paprika, and a pinch of salt and pepper until smooth.
Fold in the chicken and cheese: Add shredded chicken, 1/2 cup cheddar, and mozzarella (if using).
Stir until evenly coated. Taste and adjust seasoning.
Add optional mix-ins: Stir in crumbled bacon, diced jalapeño, or chopped celery if you like extra heat or crunch.
Stuff the peppers: Spoon the filling into each pre-baked pepper half, mounding slightly. Top with remaining 1/2 cup cheddar.
Bake: Return to the oven and bake 15–18 minutes, until the cheese is melted and bubbly and the peppers are tender.
Finish and serve: Let cool for 5 minutes.
Garnish with chopped chives or green onions. Serve with a simple side salad or steamed broccoli.