Preheat the oven to 350°F.

In a medium mixing bowl, toss together the granulated sugar, corn starch, and salt until well combined. Add the strawberries, rhubarb, and lemon juice. Toss until combined and set aside.

In another medium to large mixing bowl, combine the oats, gluten free all-purpose flour, light brown sugar, granulated sugar, cinnamon, and salt. Add the cubed cold butter, and pinch together with your fingers, until small clumps form.

Spread the strawberry rhubarb mixture evenly in a 4 quart baking dish (NOTE: You may also use a 9x9-inch square or 11x7-inch rectangular baking dish).

Top the strawberry rhubarb mixture evenly with the crisp topping mixture. Place in the oven, and bake for approximately 30-35 minutes, or until the juices are bubbling around the edges of the mixture and it is lightly golden brown.

Remove the mixture from the oven, and let cool for about 1 hour. Serve with your favorite ice cream.