Whisk preserves, 1/3 cup Cointreau and orange juice in 2-cup measuring cup. Place mascarpone cheese and 2 tablespoons Cointreau in large bowl; fold just to blend.
Using electric mixer, beat cream, sugar, vanilla, and remaining 2 tablespoons Cointreau in another large bowl to soft peaks. Stir 1/4 of whipped cream mixture into mascarpone mixture to lighten. Fold in remaining whipped cream.
Hull and slice half of strawberries. Spread 1/2 cup preserve mixture over bottom of 13X9" glass baking dish. Arrange enough ladyfingers over preserve mixture to cover bottom of dish. Spoon 3/4 cup preserve mixture over ladyfingers, then spread 2 1/2 cups mascarpone mixture over. Arrange sliced strawberries over mascarpone mixture.
Repeat layering with remaining ladyfingers, preserve mixture, and mascarpone mixture. Cover with plastic wrap and chill at least 8 hours or overnight.
Slice remaining strawberries. Arrange over tiramisu and serve.