The Phineas on Rockville Pike is an attractive, efficient restaur

Phineas, 1580 Rockville Pike. 770-0294. No reservations. Major credit cards accepted. Open 5 to 10:30 p.m. Monday through Thursday; 5 to 11 p.m. Friday and Saturday, and Noon to 9:30 on Sunday. Banquet facilities. Customers in wheel-chairs accommodated. ant that has become very successful by catering to the bottomless American appetite for primer ribs and lobster tails.

The menu at Phineas measures just five by eight inches - that's all the room needed to list seven cuts of beef, lobster, three vegetables, three deserts and "accompaniments." No appetizers or daily specials appear.

"It never changes," says one regular patron of the Phineas. "You can always count on things being the same wach time you go there."

That seems to be true, but one thing you can't always count on is getting into the Phineas, which accepts no reservations. We took our children there about 7:30 one weekday evening to find the wait was one hour.

Knowing the kids would be dozing in their ice cream if we stayed, we retreated and came back a few days later - at an earlier hour. We were asked to wait in a lounge where our drink orders wre taken, and about 30 seconds later we were ushered to our table.

The dining area of the Phineas is divided into smaller rooms with names like the Winery and the Cave, each dimly lit to create an intimate feeling. The walls hold an assortment of things including copperware, old horseshoes, camel saddles and wine casks.

I couldn't quite make out the theme and our waitress was unsure if "Phineas" referred to the one of circus fame or the fellow who went around the world.

A loaf of hot bread was delivered to our table, and the waitress suggested that because entrees are served so swiftly, we might want to delay ordering until after we visited the salad bar.

Salad bars have become so commonplace that it's difficult to find one that's impressive.This one was. The greens were very fresh and crisp, and the toppings were varied and different. These included pure white mushroom slices, cherry tomatoes, turnip slices, shredded red cabbage and bacon bits. It you don't feel like building your own salad, you can help yourself to Caesar salad.

We placed our orders, two of us choosing a smaller cut of roast beef for $6.45 and my husband opting for the "traditional cut" for $7.45. Our youngest daughter ordered from the children's menu, selecting a combination eye of the rib and lobster for $3.50.

True to her word, our waitress brought the dinners with speed. The beef was excellent, and we can assume the lobster pleased our daughter since it disappeared instantly from her plate and no bites were offered to the rest of us.

Those old favorites, popovers, the served with all meals, and as a nice touch, grown-ups get a carefe or domestic red wine with theirs. We also enjoyed the whipped cream and horseradish concoction that goes well with beef.

Extra vegetables, including a spinach casserole at 85 cents, browned potatoes at 50 cents and mushroom topaz at $1 are available but unneccessary, given the large entree portions.

Desserts offered are chocolate cheesecake, English trifle and "fresh islander ice," each at $1.

We found the service swift and attentive throughout our meal. We learned later that the Phineas is owned by the Marriot Corp. which is reputed to go to some length to train its employees, usually attractive college-age men and women.

The fact that Phineas is operated by a giant in the mass-produced, chain resttaurant field may explain why we had some feeling that the place lacks personality. Despite its good food and pleasant decor, it misses the character of a restaurant owned by individuals and where their cook is out in the kitchen trying to create new and better dishes.

Judging from the crowds at the Phineas, however, this doesn't matter to a lot of people who simply want a satisfy meal at reasonable prices.

The bill for our family came to $32.50 with tip.