Lightly grease the inside of your slow cooker with butter or cooking spray. In a medium bowl, combine the sliced peaches with 1/4 cup brown sugar, 1/2 tsp cinnamon, and lemon juice, stirring gently to coat the peaches evenly. Let this mixture sit for a few minutes while you prepare the batter—this allows the peaches to release their juices slightly, creating a more flavorful filling. Transfer the seasoned peaches to the prepared slow cooker, spreading them in an even layer.

In a separate bowl, whisk together the Bisquick, 1/4 cup brown sugar, 1/4 cup sugar, 1/2 tsp cinnamon, freshly grated nutmeg, vanilla, milk, and salt. Stir until just combined—a few small lumps are fine and will actually create a more tender topping. I prefer using freshly grated nutmeg here because it releases aromatic oils that give the cobbler a noticeably richer spice flavor compared to pre-ground nutmeg.

Pour the batter mixture evenly over the peaches in the slow cooker—don't stir it in. Cover the slow cooker with paper towels first (this absorbs excess moisture), then place the lid on top. Cook on low heat for 3 to 4 hours. The cobbler is ready when the topping is set and cooked through (a toothpick inserted into the topping should come out clean), and the peach filling should be bubbling at the edges. I like to check after 2.5 hours to get a sense of how the cobbler is progressing, since slow cookers can vary in temperature.

Remove the lid and paper towels carefully (watch out for steam), and let the cobbler cool for 5-10 minutes before serving. This resting time allows the topping to set slightly and the peach filling to thicken. Scoop into bowls and serve warm with vanilla ice cream on top if desired—the cold ice cream melting into the warm cobbler creates a wonderful contrast of temperatures and textures.