Preheat and prep: Heat your oven to 400°F (200°C). Lightly grease a 9x13-inch baking dish.
Line a plate with paper towels for the bacon.
Cook the bacon: In a skillet over medium heat, cook bacon until crisp. Transfer to the paper towels and crumble when cool. Pour off excess bacon fat if desired, but leave a thin sheen to cook optional veggies.
Optional veggie boost: If using broccoli or bell pepper, sauté in the bacon drippings for 2–3 minutes until just crisp-tender.
Set aside.
Even out the chicken: Place chicken breasts between two sheets of parchment and pound to an even 3/4-inch thickness. This helps them cook evenly and stay juicy.
Season the chicken: Rub chicken with olive oil, then sprinkle with 1/2 teaspoon salt and the black pepper. Lay the pieces in the baking dish without overlapping.
Make the ranch mixture: In a bowl, combine Greek yogurt, mayonnaise, ranch seasoning, garlic powder, onion powder, and the remaining 1/2 teaspoon salt.
Stir until smooth.
Assemble the bake: Spread the ranch mixture evenly over the chicken. Top with the cheddar and Monterey Jack. Sprinkle on the crumbled bacon, green onions, and any sautéed veggies.
Bake: Place in the oven and bake for 22–28 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and the cheese is bubbly.
If you want extra browning, broil for 1–2 minutes at the end.
Rest and garnish: Let the bake rest for 5 minutes. Garnish with extra green onions or parsley. Add a light drizzle of ranch if you like.
Serve: Pair with a side salad, roasted veggies, or baked potatoes to complete the meal.