Get a campfire started. You will need a bed of hot coals to cook your cobbler on.
Spray a Dutch oven with vegetable oil cooking spray. Add strawberries, rhubarb, lemon juice, 3/4 cup sugar, cornstarch, 1 teaspoon cinnamon and salt to the Dutch oven, stirring to coat the fruit.
Cut butter into pats, and scatter on top of the strawberry rhubarb mixture.
Combine 1/4 cup sugar and 2 teaspoons cinnamon in a small bowl or Ziploc baggie. Coat each biscuit with cinnamon sugar and place on top of the strawberry rhubarb mixture. Place the lid on top of the Dutch oven.
Place Dutch oven on bed of hot coals, making sure it is stable and even. Shovel coals onto the top of the lid to make an even thin layer.
Open the lid and check the cobbler after 5 minutes, making sure not to get coals into the Dutch oven. If one side is cooking faster than another, turn the oven. Check again every 5 minutes until the biscuits are golden and the fruit is bubbly.