It could be permissible to be vegetarianism about halal things. Although meat can be considered as a good food as well. Besides, there are some hadiths regarding eating meat. For instance it has narrated that the Prophet (SAWW) said:
We Quraish are interested persons in meat. / برقی، احمد بن محمد
بن خالد، المحاسن، محقق، مصحح، محدث، جلال الدین، ج 2، ص 451، قم، دار
الکتب الإسلامیة، چاپ دوم، 1371ق.
Or even I found another narration from Imam Jafar al Sadiq (a.s.) as the sixth Imam of Shiite school of thought who talked concerning meat that you can see it in the reference (if you are familiar in Farsi).
Anyhow, it demonstrates meat as a positive food (by observing...). But there is a nice significant point as a related rule, that is related to the harming. Actually there is a rule in Islam which says harming the body is counted as a haram practice. So you should pay heed that being vegetarianism cannot be accepted or permissible if it harms the body due to "not eating meat for a long time (for the things which are necessary for the body).