This is an add-on to my earlier comment. If you use the 10 minute rice, undercook it a little,pre-cook the celery and onion and then just mix everything together. Put it in the oven for about 15 minutes and the rice won't get mushy. They didn't post my earlier comment - what I said was this was a recipe that my mom used when I was a kid. It was easy, cheap and fed 3 kids easily.
Although this recipe made a good meal, my family and I didn't find it to be anything near over-the-top. It was fine, though - definitely something new to try. The recipe called for raw rice, but I used the 10-minute rice that I had on hand instead. I probably should have baked the dish for a shorter period because of the rice change. I've found that with meals that say to bake ground meat for a long time at a high temperature, that doing so reduces the flavor of the ingredients quite a lot. If I ever make this dish again, I will probably bake it at a lower temperature and for not as long. (I baked it for an hour at 425 originally.)