Fill a large bowl with ice water to create an ice bath.
Bring a large pot of lightly salted water to a boil. Add broccoli and cook, uncovered, until bright green and tender, about 3 minutes. Drain in a colander and immediately immerse in the ice bath for several minutes to stop the cooking process. Drain.
Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9x13-inch casserole dish with vegetable oil.
Combine broccoli, cottage cheese, eggs, Cheddar cheese, butter, flour, salt, and pepper in a large bowl. Spread into the prepared casserole dish.
Bake in the preheated oven, uncovered, until a knife inserted into the center comes out clean, 60 to 90 minutes.