Preheat oven to 375°F. Lightly grease a 12-14 inch pizza pan with butter or baking spray. Set aside.
Cream together brown sugar, butter, egg and vanilla in a medium size mixing bowl. Use an electric mixer on medium-high speed beating until creamy, about 2 minutes. Stop and scrap the bowl as needed.
To the creamed mixture add flour, oats and baking soda; beat at low speed until well mixed.
Spread dough pressing evenly onto pizza pan. Bake 12-15 minutes or until lightly golden brown. Cool completely. (Test the center with a toothpick, if needed to ensure it's cooked through.)
To make topping: Use an electric mixer to cream together cream cheese, powdered sugar and vanilla until fluffy. Add marshmallow cream, beating until fully combined and smooth. Spread over cooled crust.
Arrange fruit on top in a pretty pattern. Melt apple jelly for 5-10 seconds in the microwave and brush over all of the fruit pieces. Chill for at least 1-2 hours.
Slice and serve. May store covered and chilled for up to 2 days.