In Dutch oven or large saucepan, cook linguine as directed on package, adding broccoli during last 3 to 5 minutes of cooking time. Cook until linguine and broccoli are tender. Drain; return to Dutch oven. Cover to keep warm.
Meanwhile, in large skillet, melt margarine over medium-high heat. Add scallops and mushrooms; cook 3 minutes.
In small bowl, combine half-and-half and flour; blend well. Add flour mixture to scallop mixture; cook and stir over medium heat until mixture is bubbly and thickened and scallops are opaque.
Add scallop mixture and pesto to cooked linguine and broccoli; toss gently to coat.