Preheat your oven 375.
Layer the peaches in a 9x13 sheet pan. Spritz with lemon juice all over.
Melt 3 Tbs. of the butter in a medium bowl, then add the oats and brown sugar to it. Sprinkle the mix over the peaches. Then sprinkle the chopped pistachios over the oats, followed by the lemon zest. Take the last Tbs. of butter and pinch it into small dabs with your fingers. Then just sort of dot them over the whole crisp.
Bake for about 40 minutes (rotate at the 20-minute mark), until the peaches have softened and the oat mixture is golden brown. If any of the pistachio pieces have darkened a little too much, just flip them over before serving. ;)
Serve with vanilla ice cream!
Serves 6.
