Here’s a RideWithGPS 24 mile loop I’ve done a few times. It covers pretty much the entire island. We often extend by starting out in Orient and doing a swim at the state park after, but you can go off island, north or south fork for about any extra distance you desire. All good roads out there.

https://ridewithgps.com/routes/27957736

Having grown up on the North Fork I would recommend it for more open roads and less traffic. The geography limits you to mainly east or west travel and there are only two roads going E-W so you won’t get lost. The “Main Road” starts/ends in Greenport and goes west to Riverhead and beyond. It’s Route 25 and goes through the towns. You’ll find services, snacks and stores every few miles. A mile or two north of the Main Road is the “North Road” which goes Orient Point to Riverhead and beyond. It’s been recently repaved and the shoulder (pseudo bike lane) is in pretty good shape and plenty wide. You’ll find less stores and services on this road. It’s the road people use to get places faster.

For a nice ride I recommend you take the ferry to Greenport and ride through town to the North Road. Then head east towards Orient Point. Riding through East Marion you’ll pass the now famous Lavender Fields on the right. Expect MASSIVE traffic on summer weekends which you’ll sail past on a bike. A little further on the left is the Fork & Anchor breakfast & lunch place that’s popular because it’s the only store in East Marion. Notice there are no traffic lights in EM or Orient. The last one on Long Island is back in Greenport. Also in East Marion you can see the grave of Mark Rothko if you’re into that kind of thing. (Check the Google)

Continuing east a few miles consider taking a right at the war memorial obelisk to check out the cute hamlet of Orient. An ice cream parlor, a General Store and lots of cute historic homes dot the streets. Watch for Supreme Court Justice Sonia Sotomayor who summers here. Continue further toward the Orient yacht club and follow the road through the village. Keep going and eventually take a left to get back to the North Road in a few beautiful rural road miles. At the North Road turn right and head for Orient Point. Youll pedal to the end of Long Island and the Cross Sound Ferry dock to watch the folks going to/from Connecticut. There’s a snack shop here too. Before or after stopping at the ferry dock you could ride into Orient Point State Park. It’s 4-5 extra miles round trip on park roads, and bikes are free to enter. It’s a nice ride and worth the trip.

Since you made it to the Point head back to Greenport and the ferry. You can pull into Orient ice cream shop or the Fork & Anchor in East Marion if you need a snack. Or as you’re leaving Orient a little past the obelisk stop at the Candy Man for some very good chocolate or peanut brittle.

The whole trip is about 22 miles. Add on 4-5 miles if you go into Orient State Park. There can be a headwind/tailwind but you’ll really only notice it on the unprotected causeway that connects East Marion to Orient. Overall it’s a nice easy flat ride.

Just to clarify, my previous comments were about Orient Beach State Park. It’s entrance is on the south side of the street just before reaching the ferry terminal.

Orient Point County Park is another, slightly more difficult ride. At the end of Rt 25 instead of turning right to the ferry go straight on the road. There are signs that say “Private Road” that can be ignored because the Point Road is just past them. Take the immediate right on the “fishing road” and follow it a mile or so to the parking area. The road is all beach stone and a difficult to ride so be ready for a slow bumpy ride in a low gear. At the point you can see Plum Island, Plum Gut and both the Long Island Sound and Gardiners Bay. As you head back consider taking the grassy path on the north side that is marked Point Road. It is not a road but is easily passable by bike. A mile or so later the path will dump into a quiet neighborhood and you can make your way back to the North Road aka Rt 25.