Cut the bacon into 1-inch pieces and cook in a skillet until brown and crisp. Remove with a slotted spoon and drain on paper towels.
Preheat the oven to 350 degrees. To make the croutons, toss the cubed bread with olive oil and salt and pepper. Bake for 12-15 minutes, until croutons are crisp and golden brown.
To serve, toss the lettuce with ranch dressing and season with salt and pepper. Top with the bacon, tomatoes, and croutons.