Adjust oven rack to middle position, preheat to 350°F, and line 2 aluminum baking sheets with parchment (not wax paper).

Combine butter, vanilla, egg, brown sugar, white sugar, salt, cinnamon, and baking soda in a medium bowl. Stir until no lumps remain, then fold in rolled oats, followed by the flour, raisins and dried cranberries.

Divide into thirty 1-ounce portions with a roughly 2-tablespoon scoop and arrange on prepared baking sheets. Let stand at room temperature for at least 25 minutes, no more than 75.

Bake until pale gold around the edges, but still puffed and steamy in the center, about 15 minutes. Cool directly on baking sheets until firm, about 10 minutes. Enjoy warm, or store in airtight container up to 3 days at room temperature.