You should be able to if they are 6 weeks, and perhaps a little younger. But I would get them used to the outdoors first, especially if they are under 6 weeks. Turn off the indoor heat lamp and take them outside for short outings each day. Put a little extra "fluff" in the coop, such as a nice pile of hay, for them to snuggle into if they wish.
I have been bringing them outside for over a week now. Since our days have gotten really warm (85 today). I put them in their huge run today. They are SO HAPPY. I'm just unsure about allowing them to stay in the coop overnight. It will be a low of 53 tonight.
I would put them outside, my 13 chicks went outside when they were 3-4 weeks old, day temps 70, night 50. They were so much happier, and they just snuggled together at night. Now my chicks start outside with a heat lamp for the first few weeks.