The simple answer to that is no. The inland route, via my home town of Mortlake, or via the highway through Colac, is much quicker than the GOR but pretty much devoid of scenery. Our area is called the Western Plains for a good reason!
On the other hand, f you're keen to go to Warrnambool & Port Fairy then the inland route, Avalon - bypass around Geelong - Lismore - Mortlake, will have you in Warrnambool not long after dark ( it's about 2 1/2 hours Avalon to Warrnie that way) and you can stay in Warrnambool. Drive to Port Fairy the next day, stopping at Tower Hill maybe & on to Portland. Why do you want to go to Portland?

Hi Kwaussie--

Thanks for your help. I don't think I was clear. I know that the inland route won't be scenic. The question is whether the GOR from Port Campbell through Port Fairy, and on to Portland would be as scenic as other portions of the GOR.

I don't necessary want to go to Portland -- it's just that it looks like that's where I'd pick up the road to the Grampians.

Hi songdoc: We just did the GOR in November. Maybe you saw my trip report. Coming from Apollo Bay, we stayed overnight in Port Fairy before heading inland to the Grampians. There was some nice coastal scenery close by Port Fairy - before leaving town, we enjoyed the walk around Griffith Island just outside town as well as lovely views from The Crags, a few kilometers to the west. Leaving Port Fairy, we headed east briefly on the main road and then cut inland to Penshurst and Dunkeld. This back road was in good shape and there was very little traffic. No need to drive all the way to Portland before turning north for the mountains.

Hi RalphR: Thanks for the info--and for steering me to your wonderful trip report. That was really helpful.

What do you think of this revised plan???

Monday: overnight in Colac

Tuesday: Great Otway Park (to see those koalas!!!); then drive to Port Fairy & Griffith Island for overnight

Weds.: Head to the Grampians for (2) nights

Have to be back in Melbourne by early Friday afternoon. Will return the car in the city.

Thanks so much for your help!

OIC. I guess the answer is still no. The scenery after Port Campbell isn't nearly as spectacular.
Ralph is right, the best way up to the Grampians is via Penshurst & Dunkeld from Port Fairy, you don't need to go all the way to Portland. Be aware that there have been some major fires in the Grampians this Summer, you'll see some major devastation on the way up to Hall's Gap.
Colac is a pretty boring place to stay but I guess you don't want to be heading down into the Otways in the dark.