You could try l'Opera near the intersection of Chaussee de Tervuren and Dreve Richelle, vaguely Italian and although have not eaten there it was reliably recommended. This came after an indifferent lunch in the nearby La Sucrerie where the setting is nice but it's essentially a business restaurant attached to a hotel. Somebody else may have more on Waterloo itself which is essentially a suburb of Brussels.
Train into Brussels takes about 25 minutes but check the time of the last one back.
10 minutes by taxi will bring you in to Uccle where there are lots of restaurants - you won't go far wrong with Le Passage on Ave Carsoel for great Franco-Belge food with a modern take, also good wine list - has a michelin star but is not over-priced. Have eaten many times in il carpaccio (good Italian) and Brasserie George (athmosphere better than food) both on Chaussee de Waterloo. For something really local try Au Vieux Spijtigen Duivel (the spitting devil!) on Chaussee d'Alsemberg for authentic Belgian food and beer.