Steep 4 tbsp ground coffee in 3/4 cup boiling water in a french press for 4 minutes. Strain and set aside.
In the meantime, steep 2 chai tea bags in 3/4 cup boiling water for 5 minutes.
Combine chai and coffee, add brown sugar syrup and stir. Add oat milk and serve over ice.
If you want to make a hot latte, heat the milk in the microwave or in a small pot on the stove and add to the warm dirty chai mixture. Froth milk before adding if desired.