Combine oats, margarine, brown sugar and flour; press into bottom of 9-inch springform pan. Bake at 350 degrees F, 15 minutes Combine cream cheese, granulated sugar, peel and vanilla, mixing at medium speed on electric mixer until well blended. Add eggs, one at a time, mixing well after each addition; pour over crust. Bake at 325 degrees, 1 hour and 5 minutes. Loosen cake from rim of pan. Chill. Combine brown sugar, corn syrup and margarine in saucepan; bring to boil, stirring constantly. Remove from heat; stir in vanilla. Chill until slightly thickend. Spoon over cheesecake. Garnish with orange slice and fresh mint, if desired.