Either direction on Newport Coast (NC) is great but heres a route from my climbing class:
We start at Turtle Rock Park but you can extend it from anywhere - take Shady Hill to Summit Park turn right. Go up and over down to Turtle Ridge. Turn Left and then left again on NC. Tale NC to San Joaquin, turn right. Take SJ down to San Miguel turn right. Take it to Spyglass turn right. Take Spyglass to San Joaquin, turn left. SJ to Ridge Park turn right. Continue on RP past NC to the top and turn right on Vista Ridge. Take VR to NC turn left. Cruise down NC to Pelica Hills turn right. Up Pelican to NC turn left and then right back onto Vista Ridge. VR to Ridge Park to NC turn right. Take that to Turtle Ridge then Summit Park. Climb back up Summit Park and then turn right at Shady Hill and finish.
It's alittle over 20 miles and 4200' of climbing. An intense little ride in a short period of time. It's usually cooler near the beach and the views are spectacular!