In a large skillet, heat olive oil over medium heat. Add diced chicken. Season with salt and pepper, and sauté for 8-10 minutes until golden brown and fully cooked (internal temperature should reach 165°F).

In another skillet, fry the bacon until crispy, about 5-7 minutes. Transfer to a paper towel-lined plate to drain and cool before chopping into bite-sized pieces.

Combine the cooked chicken and chopped bacon in the skillet. Pour in ranch dressing and mix until well-coated.

Assemble the sandwiches by placing shredded lettuce on the bottom half of each bun. Add a scoop of the chicken-bacon mixture followed by diced tomatoes.

Top with the other half of the bun and press lightly. Serve immediately.