Heat oven to 350 degrees F.
Lightly oil a 9-inch round baking dish or pie plate. Thaw broccoli in skillet over medium heat. Drain well. Transfer to bowl and add red pepper and pecans. Sprinkle with salt and pepper.
In same skillet, melt 2 tablespoons butter. Whisk in mayonnaise and horseradish sauce and cook over low, stirring, to make a smooth sauce. Pour sauce over broccoli, peppers, and pecans and stir gently to coat. Spread mixture in prepared baking dish; sprinkle with breadcrumbs and cheese. Dot with remaining tablespoon butter and bake on top rack in oven for 20 – 25 minutes until golden. Serve warm.
Nutrition information per serving – calories: 179; protein: 4g; carbs: 8g; saturated fat: 5g; monounsaturated fat: 6g; polyunsaturated fat: 4g; cholesterol: 18mg; fiber: 3g; sodium 235mg.