FOUND IT: In a Penzey's catalog.
I had been waiting for the first rhubarb of the season to try this recipe. I made it last night to rave reviews.
1 cup flour
1 cup brown sugar, firmly packed
3/4 cup oatmeal, uncooked
1 stick butter, melted
2/3 cup sugar (can be replaced with Splenda)
2 tsp cinnamon
2 cups diced rhubarb (2-3 good sized stalks)
2 cups strawberries (I used more, because I had more)
1 cup water
2 tbsp cornstarch
1 tsp Vanilla
Combine flour, both sugars, oatmeal, butter, and cinnamon in a large bowl and mix until crumbly. Press half of that mixture into the bottom of a 13x9 baking dish. Spread the strawberries and rhubarb over that. In a small saucepan, combine the water, cornstarch and vanilla over medium-low heat until mixture becomes clear and thick, stirring constantly. (The recipe says this takes five minutes, it took me much less). Pour this mixture over the strawberries and rhubarb, then cover with the remaining crumb mixture, and bake in a 350 oven for 60 minutes. Serve warm with vanilla ice cream or whipped cream.