Cook linguine according to package directions. Meanwhile, sprinkle beef with salt and pepper. in a large skillet, saute beef in 2 teaspoons oil until juices run clear. Remove and keep warm.
In the same pan, saute red pepper and onion in remaining oil until tender. Add spinach and rosemary; cook and stir until spinach is wilted. Stir in cream cheese, sour cream, and milk; heat through (do not boil). Drain linguine, top with mushroom mixture and beef.