Cook pasta according to package directions; drain. Keep warm.
Meanwhile, trim fat from beef steak. Cut steak lengthwise in half and then crosswise into ⅛-inch thick strips. In wok or large nonstick skillet, heat 1 to 2 tablespoons oil over medium-high heat until hot. Add beef and garlic, half at a time, and stir-fry 1 to 2 minutes or until outside surface is no longer pink. Remove from pan with slotted spoon; season with salt and pepper. Keep warm.
In same pan, heat 1 tablespoon oil until hot. Add mushrooms and bell pepper strips; stir-fry 3 to 4 minutes or until mushrooms are tender. Remove from heat. Return beef to pan; add sliced basil and toss.
Place pasta on large deep oval platter; arrange beef mixture on pasta. Sprinkle cheese over beef and pasta or pass separately, if desired. Garnish with basil sprigs and bell pepper rings.