Heat oven to 350°F.
Combine all crust ingredients in bowl. Beat at low speed, scraping bowl often, until mixture resembles coarse crumbs. Press onto bottom of ungreased 13x9-inch baking pan. Bake 15 minutes.
Combine all filling ingredients except rhubarb in bowl. Beat at medium speed, scraping bowl often, until smooth. Stir in rhubarb.
Pour rhubarb mixture over hot, partially baked crust. Continue baking 45-55 minutes or until filling is firm to touch.
Increase oven temperature to 400°F.
Beat egg whites in bowl at low speed until foamy. Add 1/4 teaspoon salt and vanilla. Increase speed to high; beat, gradually adding 3/4 cup sugar, until glossy and stiff peaks form.
Spread meringue over hot filling, sealing to edge. Continue baking 9-11 minutes or until meringue is lightly browned. Cool completely. Store refrigerated.
*Substitute 2 (16-ounce) packages frozen chopped rhubarb, thawed, drained.