What months are the best to harvest and use rhubarb?

As long as you keep picking rhubarb you can use it all summer long

https://www.gardeningknowhow.com/edible/vegetables/rhubarb/harvesting-rhubarb.htm

• freeze it. or mix with strawberries dessert.

For the Filling

• 1 poundrhubarb stalks, trimmed and sliced 1/2-inch thick fresh or frozen
• 1/2 poundstrawberries, hulled and quartered fresh or frozen
• 1/2 cupgranulated sugar whey low
• 1-1/2 tablespoonscorn starch ??? maybe a little more
• 1 teaspoonvanilla extract

For the Topping

• 3/4 cup whole grain or all purpose flour, spooned into measuring cup and leveled-off with a knife or flour substitute
• 1/2 cuppacked light brown sugar whey low
• 2 tablespoonsgranulated sugar whey low
• 1/4 teaspoonsalt
• 6 tablespoonsunsalted butter, cut into 1/2-inch cubes
• 3/4 cupold fashioned rolled oats
• 1/2 cupchopped pecans
• 2-3 eggs optional

Instructions

It freezes well, with no blanching.