Preheat oven to 350 degrees F. For filling, in a large bowl combine cottage cheese, feta, eggs, and tapioca.
Generously butter a 13x9x2-inch baking pan. Layer 10 sheets of phyllo in pan, brushing butter between every other layer. Top with cheese filling. Repeat layering and buttering between every other layer with remaining 10 sheets of phyllo.
Bake for 30 to 35 minutes or until puffed and golden. Cool, then cut into triangles.