If you like Chinese food, there's a pretty decent Chinese place in Cohasset called Feng Shui. It's in the Stop and Shop shopping center on 3A, just about 1/10 mile past the Sohier Rd turnoff for the Music Circus. It's a nice atmosphere, and the food is tasty, although not outstanding. But, it's very convenient.
Cohasset is deepest suburbia and the dining choices reflect that. Your best bets are Tosca or Square Cafe in Hingham or Bridgeman's in Nantasket (Hull) or Saporito's in Hull for fine dining. Assuming that you can get a reservation at any of them at this point. There is Bia in Cohasset, which I have enjoyed in the past but someone recently posted that they had been disappointed there. Atlantica I do not recommend.