Notes:

• While Golden Gate Transit operates local services within Marin County, Marin Transit contracts such services to Golden Gate. Marin Transit is responsible for the scheduling and management of local bus routes, and such services may also use Marin Transit-owned buses, shown here.
• All of these buses share common features, such as reclining seats, overhead reading lights, overhead luggage racks, WiFi access, and bike racks capable of carrying either 2 or 3 bikes

These buses are used for commuter routes with high ridership between San Francisco, Marin, and Sonoma Counties. All MCI coaches feature under-storage bike racks capable of handling two bikes.

Motor Coach Industries D4500CT (45-foot) commuter bus (9xx series)
These buses have a significantly improved design compared to the earlier MCI coaches. These commuter coaches sport the latest design of Golden Gate Transit, with two buses having special designs: number 924 has the 40th anniversary decal of Golden Gate Transit, and number 901 sports a painting of the Golden Gate Bridge with the 75th anniversary decal designed by renowned Marin County-based artist John Sumner. Many of the newer coaches sport free WiFi on board, and in the future, WiFi will be progressively introduced on all these buses.

MCI D4500CT numbers 956 to 980
With this new bus type, passengers can enjoy better amenities on board, including power ports on every seat (the AC power port locations for certain seats are on the right and left bottom sides, while for most seats, those are on the bottom central portion in between seats; you will need to stoop down to find them), LED reading lights with ergonomic buttons, more enhanced air vent designs for better air conditioning and heating circulation, and an shallower stop request button.

These buses are the workhorses of Golden Gate Transit's fleet. These are used on all services operated by both Golden Gate and Marin Transit, and more than likely, these are used for basic services, some low-ridership commuter services, and local Marin County routes, as well as school day-only services within Marin County. The Orion buses, in comparison to the MCI coaches, have front-mounted bike racks, which, compared to the MCIs, are capable of carrying three (3) bikes.

New Livery
At least three Orion buses (numbers 1544, 1558, and 1571) sport the newest Golden Gate Transit design.

With Marin Transit ordering ten Gillig BRT Hybrid buses on behalf of Golden Gate Transit for its local routes, it signifies the transition from operating all high-floored buses to a mixture of high- and low-floored vehicles. Initially delivered in late 2017, these 40-footer low-floored buses (17xx series) commenced regular operations on services within Marin County in March 2018. These buses will not be used on revenue services beyond Marin County, especially on Basic Routes (Routes 30, 40, 70, and 101).

Special Liveries
A few of these Orion buses have various designs painted on them: bus number 1501 is called the "Whale Bus", also designed by John Sumner, which celebrates the importance of whales in human existence. Another limited-edition bus sports stickers, pasted by visitors to the Marin County Fair, with a focus on a certain theme.

These buses are in the reserve fleet, with a few buses transferred to Marin Transit (subsequently retired). The key differences between this model and the previous TMC model include a different wheelchair lift, capability to hold up to three bikes, harder seats (although reclining), and noisier engines.

As of 2018, at least one bus has been repainted from the original Golden Gate Transit livery to the Larkspur Ferry Shuttle livery, operating on two routes from Larkspur Ferry Terminal:

• Route 25 to Fairfax Manor via Sir Francis Drake Boulevard (peak direction only)
• Route 31 to San Rafael Transit Center (daily, connects with SMART trains to and from Santa Rosa)

The repainted bus includes one Orion V 40-footer bus (1519)