Most of these cookbooks are full view scans on Google books. Although not every one uses the word vegetarian they fit its 1847 Vegetarian Society definition (unless noted otherwise). I have made minor exceptions in some cases, namely the use of gelatin and Worcester sauce. Neither is a vegetarian ingrediant, but both are used very occasionally in a small number of otherwise vegetarian books.
The New Hydropathic Cook-Book (1854) - note: a few nonvegetarian dishes
Vegetable Diet (1859)
Principles and Practice of Vegetarian Cookery (1860)
Cassell's Vegetarian Cooking (1891)
New Vegetarian Dishes (1892)
The Fat of the Land and How to Live off it (1896)