Preheat oven to 350° F.
In a medium mixing bowl melt the butter in the microwave. Add flour, oats, Pioneer Golden Light Brown Sugar, cinnamon and allspice.
In a 9-inch square baking pan press half of the mixture into the bottom. Arrange the diced rhubarb and sliced apples evenly on top.
In a saucepan add water, white granulated Pioneer Sugar, cornstarch and vanilla. Cook over medium to medium-high heat until thick. Pour over the rhubarb and apples.
Sprinkle the remaining oat & flour mixture on the top. Bake for 1 hour.
Serve warm with ice cream or whipped cream.
Pioneer Sugar is the brand of Michigan Sugar Company, a cooperative owned by nearly 900 farmers from Michigan and Ontario, Canada. The company has been extracting pure, all-natural sugar from sugarbeets since 1906. We are proud of our past and excited about our future. Learn more about our company at www.michigansugar.com.