Melt margarine in a skillet over medium heat and cook mushrooms, spinach and onions for 5 minutes or until tender, stir continuously. Remove the skillet from heat.
In a 9 inch round pan or pie plate coated with non-stick cooking spray arrange crescent roll triangles in a circle, with narrow tips hung over the rim of the pie plate about 2 inches. Press dough onto the bottom and side of the pie plate to fill in any gaps.
In a medium bowl stir together the soup mix, half and half cream and eggs. Stir the cheese and cooked vegetables into the egg mixture until blended. Pour into the prepared crust. Fold the points of dough that are hanging over the edge back in over the filling.
Bake the quiche for 30 minutes in the preheated oven, or until a knife inserted into the center comes out clean.