Preheat and prep the pan. Heat the oven to 375°F (190°C).
Lightly grease a 9x13-inch baking dish or line it with parchment for easy cleanup.
Crisp the bacon. In a large skillet over medium heat, cook the chopped bacon until crisp, 6–8 minutes. Transfer to a paper towel–lined plate. Reserve 1 teaspoon bacon fat in the pan and discard the rest.
Season the chicken. Toss the chicken cubes with 1/2 teaspoon salt, black pepper, garlic powder, onion powder, and smoked paprika.
Sear the chicken. Add olive oil to the skillet with the reserved bacon fat.
Sear chicken over medium-high heat until lightly browned on the outside and just cooked through, 5–7 minutes. Don’t overcook—it will bake more. Remove from heat.
Make the creamy ranch base. In a large bowl, whisk Greek yogurt, light cream cheese, ranch seasoning, and chicken broth until smooth.
If it’s too thick, add a splash more broth. Taste and season with the remaining 1/2 teaspoon salt if needed.
Combine the mix-ins. Fold the cooked chicken, half the bacon, 1 cup cheddar, Parmesan, broccoli, and most of the green onions into the ranch mixture. Stir until evenly coated.
Assemble. Spread the mixture in the baking dish.
Top with the remaining 1/2 cup cheddar and the rest of the bacon.
Bake. Bake uncovered for 20–25 minutes, until the casserole is bubbling at the edges and the cheese is melted and lightly golden.
Finish and serve. Let it rest 5 minutes. Sprinkle the remaining green onions on top. Serve with a crisp side salad or over cauliflower rice for extra volume.