In a medium mixing bowl, stir together the flour, oats, brown sugar, baking powder, and salt.
Pour in the melted butter and stir until the mixture looks crumbly. Set aside.
Filling
Cut the strawberries in half lengthwise and place them into a mixing bowl. Add in the cornstarch, sugar, lemon juice, lemon zest, and vanilla. Toss until the strawberries are evenly coated.
Pour the strawberries into a 2-quart baking dish and spread the berries into an even layer. Sprinkle the topping all over the strawberries until they are evenly covered.
Bake for 30-35 minutes or until the topping is golden and the strawberries are bubbling along the edges.
Remove from the oven and cool for 10 minutes before serving. We like to top this strawberry crisp with a scoop of vanilla ice cream.
Notes
If you want to make a strawberry crumble instead of a strawberry crisp, leave out the oats and add another 1/2 cup of flour. This gives a streusel-like topping to the dessert.
If you don’t have fresh strawberries available you can use frozen ones instead. Just add an extra 1/2 tablespoon of cornstarch to the filling mixture with the frozen strawberries.