1Place bacon in a large, deep skillet, and cook over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain bacon slices on a paper towel-lined plate; crumble bacon.
2Combine broccoli, red onion, raisins, mushrooms, sunflower seeds, and crumbled bacon in a large bowl.
3Mix mayonnaise, sugar, vinegar, salt, and black pepper in a bowl until well blended.
4Pour mayonnaise mixture over vegetables; toss to coat.