Maintaining a vegetarian diet in Portugal is not easy. Most restaurant will offer you fish if you don’t want meat. There are a number of really good ones in Lisbon, thou. Terra has a giant all you can eat buffet and a lush garden to enjoy you food in.
Eating out as a vegetarian in Peniche is a different story. Nagoya Sushi has some tofu and vegetarian sushi on offer and Brunos bar serves a delicious veggie burger. Most other restaurants (except for pizza) will offer you a salad or an egg omelette. Always tell the waiter to make yours without ham.
Pizza/Pasta/Risotto at Cantina are always a save choice.