Brown ground beef with onion and mushrooms in a skillet over medium heat; drain. Stir in broccoli and cheese. When cheese is melted, stir in sour cream.
Line a lightly greased 13"x9" pan with one tube crescent rolls. Spoon ground beef mixture over rolls; arrange remaining of tube rolls on top.
Bake, uncovered, at 350° for 15 minutes or until golden. Cut into squares to serve.