I used oolong tea in a ~1.050 rice adjunct lager. I cold steeped 4 oz of tea in a French press for about 36-48 hours and added to 5 gallons of finished beer. The tea character is pretty strong but the base beer is very transparent. I added sake as well which muddles the perception of the tea a bit. If I attempt again, I will cut the tea down to 2-3 oz but would consider 4 in a darker, stronger, more complex beer.
Definitely choose your tea wisely. The oolong has a nice herbal, fruity character but I almost used a green tea which I think would have added an undesirable grassy, vegetal flavor after tasting the two teas side by side.