To make the peaches: In a medium bowl, toss peaches with lemon juice. Add all other ingredients and toss evenly to coat. Transfer mixture to prepared baking dish and spread evenly. Set aside.
Bake for 30-40 minutes, until topping is golden brown and juices are bubbling. The peaches should be tender, but not mushy. Allow to cool for a few minutes on a wire rack until warm. Serve warm and, if you like, add ice cream or whipped cream.
Crisp will keep, covered, in the refrigerated for up to 3 days, but will taste best on the first day it’s made, when the topping is still crispy. After that, it will slowly become soggier.