Add the bacon slices to a large skillet and set over medium heat. Cook, flipping occasionally, until slices are crispy.
Remove and drain on paper towels.
Meanwhile, toast the four slices of bread. When done, butter one side of each slice of bread. Top the buttered side of each with one slice of bacon broken in half crosswise, a quarter of the chopped sun-dried tomatoes, and a quarter of the sliced avocado. Season with salt and pepper.